Using Batted Ball Data in Scouting

Chris Carter has the longest average fly ball time at 5.47 seconds. (via Arturo Pardavila III)

Chris Carter has the longest average fly ball time at 5.47 seconds. (via Arturo Pardavila III)

Editor’s Note: This piece was initially given as a presentation at the marvelous 2015 Saber Seminar.

Scouts have been trying to measure a hitter’s power for years. The best way they have found is to show up to the ballpark two to three hours early and catch batting practice. Then they judge how far the player can hit the ball and give the player a power rating from 20 to 80. This isn’t a foolproof plan, however. Sometimes you can’t get to the ballpark in time, sometimes there is no batting practice, or sometimes the player you want to see doesn’t take batting practice. Stuff happens, in other words. And even if you do get to see the player you want in BP, it is tough get readings on a player with just a few swings of the bat. Maybe the player isn’t as good as you thought, or maybe said player is working on something other than “hit the ball as hard as you can.” But, by using some batted ball information that has become available over the past few seasons, some new ways are potentially available to measure a hitter’s power.

Two available pieces of information are fly ball hang times and batted ball velocities. Inside Edge tracks fly ball hang times, but we have not found many ways to use that data until now. The batted ball velocity data, as you may know, is just becoming available to the public this season. I don’t feel the best about jumping to any conclusions with just part of a year’s worth of data, but some information is better than nothing. Analyzing both pieces of data will be a nice starting point for further discussion and research.

In attempting to use these tools to measure a prospect’s power potential, I used the power values provided by FanGraphs lead prospect analyst Kiley McDaniel—Game and Raw—for prospects who have been promoted to the majors this season. Additional information on his power ratings can be found in this article. I collected the prospect power values (and the rest of the data) on July 21, so the values will not line up with the player’s current stats. Again, I know this is not even close to being a perfect amount of data to draw any long-standing conclusions. But it is a starting point which can be refined as more data become available.

Hang Time

Until recently, I have never considered those towering infield fly balls to be useful for anything except to see how hard the hitter can slam his bat to the ground in frustration or the possible collision of a couple of non-communicating fielders (which is always funny). However, the amount of time a ball stays in the air can contain some useful information. By filtering only the outfield fly balls, here are the top players in average and max flyball time (minimum 600 plate appearances from 2012 to 2015):

Average Fly Ball Times

  1. Chris Carter: 5.47 seconds
  2. Adam Dunn: 5.39
  3. Jason Bay: 5.38
  4. Dan Uggla: 5.38
  5. Giancarlo Stanton: 5.36

Maximum Fly Ball Times

  1. Dayan Viciedo: 8.7
  2. Mike Trout: 7.8
  3. Justin Ruggiano: 7.8
  4. (T) Mike Napoli, Alex Rodriguez, J.J. Hardy: 7.7

For an example, here is the 7.8 second Trout fly ball.


It takes a fairly decent power hitter to average over five seconds on his fly balls, or to even hit just one that spends more than seven seconds in the air.

Now, it is time to put some everyday stats behind the fly ball times.  Here are R-squared values for isolate power (ISO), home runs per fly ball (HR/FB) and homers per 600 plate appearances (HR/600 PA) compared to the two fly ball values (minimum 200 PA per season):

Types of Time ISO HR/FB HR/600 PA
Average Fly Ball Time 0.320 0.29 0.36
Max Fly Ball Time 0.210 0.21 0.24

The R-squared values aren’t the greatest, but the there is definitely a slope to the data. I bucketed the hang times to get some average power values and put all the players’ average flyball values into a range. Additionally, I matched up the scout grades from Kiley’s scouting table based on the HR/600 PA values:

Max Fly Ball ISO HR/FB HR/600 PA Scout Grade
  >= 7.4 0.200 16.8% 25.3 60
7.2 -7.3 0.200 16.1% 25.5 60
 7.0-7.1 0.190 14.8% 22.9 55
 6.8-6.9 0.171 12.7% 19.4 55
 6.6-6.7 0.154 11.1% 16.4 50
 6.4-6.5 0.137  9.3% 13.5 45
 6.2-6.3 0.118  7.3% 10.0 40
 6.0-6.1 0.104  5.9%  8.2 40
   < 6.0 0.104  5.8%  7.9 35

To have major league power, a hitter may need to be able to hit a fly ball with enough “oomph” to have it fly for six seconds or more.  Additionally, the hitter’s average fly ball times need to be at or over 4.5 seconds.

Now that we have some historical perspectives, it is time to line up the fly ball values with Kiley’s scouting power grades for this year’s rookie class. While I have four years’ worth of fly ball data, Kiley has been at FanGraphs for only one prospect ranking cycle. I took the rookies with at least 50 plate appearances and I ended up with 33 players. Not a ton of players, but here is how their current game and raw powers grades line up with the fly ball times:

Game Power Average Flyball Time Max Flyball Time ISO HR/FB HR/600 PA
55-60 5.1 7.1 0.173 16.2% 18.3
45-50 5.1 6.8 0.175 18.3% 23.0
35-40 5.0 6.2 0.129  9.0% 12.7
   30 4.8 6.3 0.097  6.8%  8.9
   20 4.9 6.5 0.132  8.1% 11.2

Raw Power Average Flyball Time Max Flyball Time ISO HR/FB HR/600 PA
65-80 5.1 7.1 0.173 16.2% 18.3
   60 5.0 6.6 0.173 14.5% 19.7
   55 5.2 6.6 0.162 16.7% 20.4
   50 4.9 6.2 0.116  8.0% 11.3
   45 4.8 6.2 0.094  3.5%  4.9
  <40 4.8 6.3 0.091  5.7%  7.4

While dealing with this small sample of prospects, there is a definite dividing line between 40 and 45 game power and 50 and 55 raw power. An average fly ball time of over 5.0 seconds puts the player into 20 home run territory (ie, (above average power). Also, a player who hits a single fly ball in the air over 6.5 seconds is likely to be in that same 20 home run range.

Looking over the players Kiley graded, a few don’t have scouting power scores that line up well with their 2015 results. The first is Carlos Correa. His game power is at 20, which is barely serviceable as a major league player. Correa has hit a fly ball at 7.1 seconds and is averaging 5.2 seconds on his fly balls. This would put his power in the 55-60 range, not in the Jarrod Dyson-like 20 power range. So far this season Correa has hit decently. He is on pace for 31 home runs, a .241 ISO and 22 percent HR/FB over a full season. The other players Kiley may have been a little conservative on are Joc Pederson and Steven Souza who both got a below average power grade of 45,  have average fly ball times of 5.3 and max fly ball times of 7.1. Each of those values indicate above average power.

To use these values for scouting, I would concentrate on the maximum value range. Scouts are usually starting their stopwatches at the point of contact for a time-to-first measurement. A player is not sprinting to first base on a high towering fly ball, so the scout can let the stopwatch go until the ball eventually lands. Since, I started tracking these numbers on the amateur level early this summer, I have seen only one ex-major leaguer hit one over 6.2 seconds. The best top values have been generally in the 5.5-second range.

It is easy to time the ball from the moment of contact and get a good reading. For people who will see a player several times, a hitter’s average value can be tracked. It is far from a perfect method to determine a hitter’s power, but it is just one more possible data point to help with evaluation.

Batted Ball Velocity Data

The data the public has been waiting a few years for is now available: batted ball velocity. While I have seen the data tracked for hitters by scouting services, there has never really been a reference point for what is or isn’t a good value. Well, now some data can be collected and used. Here are the R-squared values comparing HR/600 PA, ISO and HR/FB to a player’s max velocity, average velocity and average fly ball/line drive velocity (minimum 50 plate appearances):

Velocity HR/600 PA ISO HR/FB
Max Velocity 0.13 0.17 0.17
Avg Velocity 0.09 0.11 0.09
Avg FB/LD Velocity 0.09 0.11 0.09

Not great R-squared values, but again, a slope does exist.

Let’s look at the actual values of the velocity information below. I bucketed these just like the fly ball times. One item that sticks out immediately is that only one hitter has a maximum velocity under 100 mph (Tyler Flowers). A key maximum exit velocity to begin to take notice on is anything over 108 mph — that is the league average. The average values create better results in that they smoothly change from one value to the next:

Max Velo HR/600 PA ISO HR/FB Scouting Rank
  >116* 32.2 0.242 21.6% 70
114-115 21.2 0.177 16.0% 55
112-113 20.7 0.178 14.0% 55
110-111 16.5 0.154 11.7% 50
108-109 15.9 0.155 10.7% 50
106-107 11.0 0.120  7.5% 40
104-105  9.7 0.108  6.4% 40
   <104  8.3 0.103  5.3% 35
* Giancarlo Stanton

AVG Velo HR/600 PA ISO HR/FB Scouting Rank
> 94* 50.9 0.341 32.1% 80
   93 26.5 0.221 19.9% 65
   92 27.6 0.215 17.5% 65
   91 19.2 0.175 14.5% 55
   90 19.0 0.172 13.4% 55
   89 17.8 0.157 12.5% 50
   88 15.0 0.147 10.7% 50
   87 12.9 0.131  8.8% 45
   86 11.4 0.122  8.0% 40
   85 11.1 0.117  6.9% 40
   84  6.5 0.091  4.2% 35
  <84  5.2 0.089  3.7% 35
* Giancarlo Stanton

LD/FB Velocity HR/600 PA ISO HR/FB Scouting Rank
  >98 50.9 0.341 32.1% 80
96-97 20.3 0.180 14.3% 55
94-95 19.9 0.179 14.0% 55
92-93 15.7 0.150 10.9% 50
90-91 15.2 0.145 10.6% 50
88-89 13.0 0.131  8.9% 45
86-87 11.7 0.121  7.3% 40
  <86  7.1 0.090  5.0% 35

Note: Giancarlo Stanton is hella good. Now, here is how the batted ball velocity values line up with the ranked prospects.

Raw Power Max Exit Avg Exit AVG FB/LD Exit ISO HR/FB HR/600 PA
     65-80 112.8 90.9 96.1 0.173 16.2% 18.3
        60 110.5 89.2 93.2 0.173 14.5% 19.7
        55 111.5 89.8 94.4 0.162 16.7% 20.4
        50 108.7 87.9 90.0 0.116  8.0% 11.3
        45 108.0 85.4 89.4 0.094  3.5%  4.9
40 or less 106.0 85.9 88.0 0.091  5.7%  7.4

Game Power Max Exit Avg Exit AVG FB/LD Exit ISO HR/FB HR/600 PA
55-60 112.8 90.9 96.1 0.173 16.2% 18.3
45-50 111.7 90.3 96.0 0.175 18.3% 23.0
35-40 107.7 87.3 89.8 0.129  9.0% 12.7
   30 108.6 87.6 90.4 0.097  6.8%  8.9
   20 108.4 86.4 89.7 0.132  8.1% 11.2

The splits are obvious. A player with a maximum exit speed over 110 translates to having above average raw power (55 or more) or average or better game power (45 or more). The two average exit velocity values, total and FB/LD, are also broken up at the same 55/45 levels.

Now comes the problem for scouts: How can they use these major league values in parks without pitch speed detection cameras? In addition, as we have discussed, a perfect time to evaluate hitters is during practice, but the batted ball speed is always greater than the pitch speed. In batting practice, a hitter can really tee off on the incoming meatballs and add some batted ball velocity. One roadblock to this method is the batting practice pitch speed. Professor Alan Nathan has determined pitch speed has some effect on batted ball velocity. The effect is only a sixth that of the bat speed, but it is not negligible.

Another possible source is in showcase or prospect events. These events, such as this showcase put on by Prep Baseball Report, have started to track batted ball velocity. This isn’t foolproof — for instance, the hitters are usually hitting off a tee. And the measurements may not be as sophisticated as those in major league parks. But it’s a start.

As for which batted balls to track, I think the key value will be the maximum velocity. Unless a team is able to track its own values over several games or hitting practices, the values will probably be useless. I am wondering if a maximum batting practice value could be tracked for players. At this point, the scout is seeing the ball travel and giving the player a traditional power ranking by how far the ball travels. This method for tracking power can be done, but it takes a little more work and possibly a second radar gun (which isn’t optimal).


After going over some batted ball information, it seems like fly ball times and batted ball exit velocity may be a good way to help measure a player’s power. The results are not perfect, but with the limited amount of data available, I am surprised that the results worked out as well as they did. Overall, the average values give a better indication of the player’s true ability, but it would be hard to track. Instead, we could use the maximum values, or instances when a certain value is reached — like 6.0 seconds for a fly ball in the air or an exit velocity of 100 mph or more.

I have just begun putting this information together and I believe so much more can be learned. I think teams may have already been doing this work, as they have had the data for years and with larger budgets than FanGraphs. I think the key will be to go back and re-examine this information in about a year and half. At that point, two sets of batted ball data will be available for correlation and I (and others) can begin to put the preceding information through more rigorous tests. I look forward to checking some of my conclusions.

References & Resources

Jeff, one of the authors of the fantasy baseball guide,The Process, writes for RotoGraphs, The Hardball Times, Rotowire, Baseball America, and BaseballHQ. He has been nominated for two SABR Analytics Research Award for Contemporary Analysis and won it in 2013 in tandem with Bill Petti. He has won four FSWA Awards including on for his Mining the News series. He's won Tout Wars three times, LABR once, and got his first NFBC Main Event win in 2021. Follow him on Twitter @jeffwzimmerman.
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6 years ago

Great stuff, Jeff!

6 years ago

Using hang-time as a scouting tool is a brilliant idea, since it incorporates both loft and batted-ball velocity. From looking at your data, and based upon results I’ve seen on batted-ball velocity, it would probably make sense to average out the highest values (say the top 25%) in order to get the best read on power. So if a scout gets a chance to time a dozen fly balls from a prospect, averaging the three longest hang times might be the best indicator.

Thanks for another great article.

6 years ago

Good stuff…I will say veteran scouts have been timing high pop ups for many many years as a possible indicator for power. But typically it is treated more as an interesting aside, rather than a hard and fast indication.

Jetsy Extrano
6 years ago

So the complication you’re dealing with is that hang time comes both from hitting the ball hard, which is good for power, and from hitting the ball straight up, which is bad.

Using max hang time is really clever, on the idea that everybody hits some at a high angle, so we can roughly isolate how hard they hit. I would want that to work better as a proxy for power than average hang time, which may signal can-of-corn hitter…

But how much energy a batter gets into the ball depends on the launch angle. You get more by hitting it square on, back out at your swing angle. So the guys who get the most energy into their high popups, maybe their swings aren’t tuned to get the most energy into the balls hit at a good home run angle, 25-30 degrees.

Interesting stuff.

Alan Nathan
6 years ago

In the interest of full disclosure, I have expressed by skepticism about this topic to Jeff privately a month or so ago. I now would like to open this up to the rest of the readers.

It seems to me that the most direct measure of power is exit speed. A large exit speed means that the swing speed is large and the ball is reasonably well squared up. A large exit speed does not necessarily mean there will be a lot of home runs, since that requires both a large exit speed and a launch angle ideally in the 25-35 degree range. But a large exit speed will lead to higher babip, regardless of launch angle.

On the other hand, what does a big hang time imply? It implies that the vertical component of the exit speed is high. For example, a 100 mph exit speed at 50 degrees will have the same vertical component as a 80 mph exit speed at 73 degrees. They will both have approximately the same hang time. But an 80 mph exit speed is pretty modest. My conclusion is that I don’t see how a big hang time necessarily is a reflection of good power.

That is the argument I present privately to Jeff. I am not claiming he is wrong. I am claiming that, based on the argument I have presented, I am skeptical. As always, I am willing to be persuaded otherwise, so please educate me on this matter.

6 years ago
Reply to  Alan Nathan

I see your point about exit speed being the far better value to use, provided you have a way to accurately measure it. As Jeff points out, for use as a scouting tool you would only need a stopwatch to measure hang time, but you might not be able to get an accurate read on exit speed at many parks (at least not yet).

Your point about the extreme exit angle/mediocre exit speed combination is very relevant, however. If we limited the hang-time measurements to balls hit to the outfield (say 250 feet or more), how likely would it be to generate a lot of hang time on a ball hit 80-85MPH?

Alan Nathan
6 years ago
Reply to  tz

tz: What you suggest would certainly help. From a purely analytical point of view, since we have Statcast data on exit speed and Inside Edge data on hang time, why not look directly at how those two quantities are correlated, looking at averages quantities for each batter?

Chris Mitchell
6 years ago
Reply to  Alan Nathan

I agree that it would be interesting to see the relationship between hang time and exit velocity. owever, doing so by batter might not be ideal given the holes in the Statcast data (I don’t know enough about the quality of the data to say for sure, but just speculating). In any event, I think doing so at the ball-in-play level would be revealing.

Peter Jensen
6 years ago
Reply to  Jeff Zimmerman

Jeff – Your answer to Alan shows that you still don’t understand. Players that have good power will unquestionably have high maximum exit speeds and long hang times. But that does not imply that players that have high exit speeds or long hang times have good power. Players that have long hang times and high exit speeds but have poor pitch recognition or hit too many fly balls that don’t leave the park don’t make it to the big leagues in the first place or don’t stay very long if they do. Your study is misleading because of serious survival bias and aforementioned fact that correlation does not imply causation. Scouts are already doing a pretty good job of assessing power as your charts suggest. Incorporating maximum exit speed or hang time puts the emphasis on the wrong “new” data and would not improve their evaluations. Tracking the percentage of hit balls that a prospect hits between 10 degrees and 20 degrees is the best path to better evaluations.

And please put the N number of batters in charts where it is appropriate.

Cool Lester Smooth
6 years ago

I do think it’s worth noting that Correa’s hang time lines up very well with Kiley’s “present raw power” grade of 60.

It looks like he just got to it in games a little more quickly than people were expecting, haha.

Peter Jensen
6 years ago

This is an unsuccessful article on a number of levels. It is a perfect example of how even an experience analyst can err when he forgets that correlation is not causation. The key statement in the article is “One item that sticks out immediately is that only one hitter has a maximum velocity under 100 mph (Tyler Flowers).” One hundred miles per is plenty of exit speed to hit a home run if it is hit at the proper vertical angle which means that almost every major league hitter has the swing speed necessary to hit home runs. Having a higher maximum exit speed is beneficial because it is an indication that a batter is capable of a greater swing speed, but a greater swing maximum swing speed is a redundancy that is meaningless unless a batter actually hits the ball squarely more times so that that swing speed is translated into exit speed. To say that another way, it is more productive to hit the ball 100 MPH at 15 degrees vertical angle 40 % of the time than it is to hit the ball 90 MPH 20% of the time and 110 MPH at 25 degrees 20 % of the time. Even though the 2nd player would have a greater maximum exit speed and longer hang times.

The reason scouts like to observe batting practice is not because they want to find players that can hit the longest home runs, but they want to find players that can swing hard and consistently hit the ball squarely. That is the necessary skill. It still may not be sufficient skill to make a major league player. A batter needs to demonstrate that he can still swing hard and hit the ball squarely during game conditions and that is why most progressive major league teams have installed Hit Fx cameras in their minor league parks.