Do Southpaws Take Longer to Mature?

The road to my question today began half a century ago—or a year and a half ago, depending on how you count it.

The nearer origin was Frank Jackson’s piece in the Hardball Times Baseball Annual 2016, titled, “There’s Always a Reason to Go.” The origin of his essay was a game he attended at the end of the 1966 season, meaningless to the home Phillies but vital to the visiting Dodgers, looking to clinch the pennant. Unknown to virtually everyone at the time, it would become historic for another cause: the last regular-season game Sandy Koufax ever played.

Musing on Koufax’s brilliant but truncated run of glory, Jackson wrote:

He is the ultimate poster boy for all those erratic left-handed pitchers who test the patience of their team’s management. Since southpaws are fewer in number than right-handers and typically take longer to mature, most teams will stick with them longer. No team was rewarded more for its patience that the Dodgers in the later 1950s and early 1960s.

The assertion in the middle sentence has been rattling around in the back of my brain ever since. Left-handed pitchers are clearly more scarce than right-handed pitchers. Whether they take longer to mature is not as clear.

I could just take a fellow THT writer at his word on something that sounds pretty plausible. I could also take apart the claim and see whether it holds up, because that’s what I would do if I heard it from any other source. No gold stars will be awarded for guessing which one I am doing.

To figure out which group takes longer to mature, I need to look at entire careers if possible. For my data set, I selected every pitcher who debuted in the major leagues between 1996 and 1998. That range was a compromise, both avoiding the warping effects of the 1994-95 strike years and maximizing the chances the chosen pitchers’ careers would be complete.

It turns out just one pitcher in that range lasted into the 2017 season: Bartolo Colón. He’s the only pitcher in the study, of either handedness, to pitch at age 41, or 42, or 43. Or 44, though his stats for the current season obviously are not included in this study.

Some pitchers had to be removed from the sample. Several were position players throwing an inning or two, which goes against the purpose of looking at pitcher development. Others were from countries whose circumstances distorted examination of their development, specifically Japan and Cuba. For Japan, it was because having to play for a long time in NPB before crossing the ocean cut off much of the development we’re supposed to be looking at. For Cuba, it was because their entry into the majors depended greatly on when they were able to defect, again skewing the development curve.

(I made one exception. Vladimir Núñez was born in Havana in 1975 but left Cuba young enough that he attended high school in the Dominican Republic. I decided this made his development as a pitcher normal enough to keep him in the sample.)

This bit of weeding left me with 85 left-handed and 195 right-handed pitchers. I recorded the ages of their MLB seasons and several performance stats from each year. These were ERA, FIP, walk and strikeout rates (all adjusted to league averages), plus bWAR. I also recorded batters faced for each season, finding this a little more precise than innings pitched. (In high-offense years, one inning pitched can mean a higher number of batters faced than in low-scoring years. Total pitches would be ideal, but that’s not available for earlier years.)

I will give the number of pitchers in the majors and the batters they faced for the full range of ages, left-handed and right-handed. This is mainly to show you where sample sizes may be too small to be reliable.

The data probably will be most reliable between ages 22 and 35, as pitchers in the majors are less than a tenth of the full sample before and after that range. The four years longer that righties pitch in MLB are almost exclusively due to Colón. That speaks exclusively to his own personal gifts, not to righties or lefties in general.

Some patterns emerge before any examination of age. First, the ’96-’98 right-handers pitched more than their left-handed counterparts. The margin of 334,169 batters faced to 97,723 outstrips both the ratio of righty to lefty pitchers (195 to 85) and the ratio of MLB seasons posted by both groups, 999 to 403 in the righties’ favor. The righties have 49 percent more batters faced per career, and 38 percent more BF per season. (They also have longer careers than lefties counting by seasons, 5.12 to 4.74.)

This derives from how southpaws have been used over the last 20 years. Every bullpen seems to need at least two left-handed options, including one who is a pure left-on-left specialist. Both those trends lead to left-handers pitching to fewer batters. While lefties thus become sought after, it’s in a role that renders them fungible, easily discarded should they turn ineffective for a while. Jackson’s statement that teams stick with southpaws longer is possibly true for the subset of starting pitchers, but in general is untrue, or at least superseded by modern doctrines.

The right-handers are also more effective pitchers, at least going by Baseball-Reference’s version of WAR. The ’96-’98 righties accumulated 665.5 bWAR over their careers against just 147.6 bWAR for the left-handers. Measuring per career, per season, or per batter faced, the righties had a better WAR rate. (For example, righties posted 1.99 bWAR per 1000 batters faced while lefties managed 1.51 bWAR/KBF.)

While interesting, these aren’t the facts I was trying to unearth. They do, however, guide my look at the pace of pitcher maturation. They are a reminder to judge the two groups by their own peaks and valleys, not only against each other’s performance.

The simplest measure of maturation is to count how many of our sampled pitchers were playing in the majors at various ages. This chart shows the percentage of each handedness of pitchers in MLB at each age, from 20 to Bartolo.

Going by a single standard, the righties could be said to mature marginally sooner. Right-handers have more than 50 percent of their cohort in the majors from ages 24 to 27, while left-handers manage it only at age 26. Make the cutoff 40 percent, however, and they both have the same range, from 24 to 28. With the cutoff at 33 percent, they are even again, from ages 24 to 29.

Go by separate standards, and again the lefties mature marginally later, perhaps. The lefties’ single-year peak comes a year later than the righties’ (26 to 25), and this holds for two-year (26-27 to 25-26) and four-year (25-28 to 24-27) peaks as well. For three-year peaks the age ranges are identical, and this holds also for peaks of five, six, and eight years. (A tie in the left-handers’ numbers meant they didn’t have a seven-year peak as such.)

Lefties do have a greater presence in the majors during their mid-30s, but the margin is not great. It’s also balanced by a larger righty presence during the early-30s, with a bigger margin while it lasts. These two events roughly cancel out.

By mere presence in the majors, the southpaws may mature later, though it looks like a matter of months instead of years. More telling should be the patterns of performance in the majors, and there are several ways we can look at this.

I will start with batters faced, a simple look at how much confidence their teams have in sending them to, and keeping them on, the mound. First is batters faced per pitcher in the sample, whether or not he’s in the majors yet. (I’d say a BF of zero speaks to the confidence your parent club has in you.)

Righties have the higher BF rates, which we knew already. The peak values for both hands come from age 24 to age 27, with the righty peak perhaps stretching to age 28. No clear difference, and the unclear difference would have lefties maturing a touch earlier, not later.

Next is batters faced per pitcher in the majors.

The lefties’ peak comes at age 22, but with just nine pitchers from the full left-handed sample of 85 in MLB at that age, this probably should be discounted. Even with that done, the long peak comes much earlier for lefties than righties. The huge spike in the 40s for right-handers is, of course, Colón’s solo act, discounted statistically.

The batters-faced method does not support the theory of later lefty maturation, at least as far as innings pitched tracks with maturing as a pitcher.

We’ll look next at walks and strikeouts, which have a more direct connection with pitching performance. I adjusted both to the league and year, putting them on plus scales (BB+ and K+) where 100 is the average and higher means more of each.

Right-handers’ wildness is clearly concentrated in their youth, while left-handers need much longer to shake off theirs, and arguably never quite do. That’s true whether you are measuring them against righties or against themselves. (The late righty plunge is all Colón and his excellent command. Indeed, everything from 40 onward for righties is all Colón.)

This is the strongest evidence yet of later maturation for southpaws, and, fittingly, it tracks with how Koufax himself turned the corner. For his first six seasons, Koufax’s walks-per-nine-innings rate was never lower than 4.4. In 1961, at age 25, he drove it down to 3.4, and within two more years would have it at half of that. His strikeout rate stayed fairly steady as he did so, but his total strikeouts spiked as he was trusted with more innings. He would lead the majors in punchouts with 269 in 1961, the year he became what we think of when we hear the name Koufax.

For strikeouts, youth is served in both cases. K rates ride high early, then pick a year in which to make a long-term drop. The drop age for lefties is 28; for righties, it’s 29. We must count this as evidence against the theory. One could also point to how the lefties exhibit a mid-thirties Indian summer (note: I don’t mean going to Progressive Field in July). However, the sample size there is small enough (10 pitchers at age 35, and eight at age 36) to give it diminished weight.

Walks agree with our hypothesis, but strikeouts disagree. Next we’ll look at ERA and its cousin FIP. I figured both in plus terms, mainly for my ease of calculation. Just remember that higher is better, as it was for strikeouts (but not walks). Also, be aware of the truncated vertical axes for ERA+ and FIP+, done to make movements more discernible.

Results for ERA+ are fairly clear. The right-handers break out to a higher level at age 26, while for the left-handers the breakthrough comes at age 30. That’s exactly the type of pattern we are looking for—which makes the following chart all the odder.

For FIP+, the lefties do well early before dropping off at age 25, only spottily climbing back well into the 30s. Right-handers show a more expected progression, making a big step up at age 26 just as the ERA+ numbers did. I don’t have an explanation for the lefties’ divergence between ERA+ and FIP+ patterns, or for why their FIP+ underperforms their ERA+. (Or is ERA out-performing FIP?) In any case, it’s a mark against the case for late lefty maturation, though perhaps smaller than the ERA+ mark in its favor.

Finally, we’ll look at the bWAR measures. First up is the ratio of WAR to all pitchers in the respective handedness samples.

The left-handers peak from ages 23 to 27, with an added bump at 30. The right-handers peak from ages 25 to 30. This is a clear example of southpaws maturing first, or at least their numbers doing so.

When we shift to counting only the pitchers in the majors, things get much wilder. I cut off the vertical axis at 2 bWAR per pitcher, due to a couple Colón years, to keep the scale manageable.

There is no obvious peak for the lefties: one can make cases for their peak starting at age 21 or ending at age 36. The righties are somewhat clearer, with their five best non-Colón seasons coming between ages 29 and 34. Making a definitive statement one way or the other would be tough, but claiming lefties mature later than 29 to 34 would be next to impossible.

My third and last angle on bWAR examines it as a rate statistic, measured against every 1000 batters faced by the pitchers.

The right-handers have a long plateau from ages 26 to 35, with an age-34 spike (and a couple of Colón spikes). The left-handers peak both earlier and later. Their first peak, 20 to 24, partly can be discounted for small samples at the youngest ages, but the 23-24 sub-peak is more genuine. A later peak range arrives at ages 30 to 36, meaning the southpaws peak both before and after the righties. Once more, a distinct pattern does not emerge.

Where does this cascade of charts and figures leave us? Three of the categories—walks, ERA, and percentage of sampled pitchers being in the majors—indicate a later peak for left-handed pitchers, the latter somewhat more mildly than the others. Four other categories—batters faced per pitcher in the bigs, strikeouts, FIP, and bWAR rate for all sampled pitchers—indicate the opposite is true. The remaining three categories gave no useful evidence.

Even if we drop the batters-faced-per-pitcher ratios, easily dominated by modern bullpen strategy rather than actual talent and performance, that leaves the score at three to three. Positive evidence from walks is offset by the strikeout numbers; ERA is likewise countered by FIP. The positive categories show somewhat stronger trends, but not enough so to change the conclusion.

The theory that left-handed pitchers take longer to mature than right-handed pitchers is not true. At the least, the effect is so subtle that it cannot clearly be found within the wide net I cast for corroborating data.

I was afraid this would happen. I’ve wound up contradicting the statement of a fellow Hardball Times writer, whose fine work does not merit the “gotcha” treatment. Frank Jackson should take as consolation that I am liable to give this treatment to anybody, all the way up to Bill James and The Glory of Their Times. Indeed, I’ve done this to myself, and more than once!

If Jackson erred, it was perhaps in being seduced by a tempting narrative. (An old story-writer like myself has nothing against narratives, but fiction can be much neater than reality usually is.) The belief that southpaws take longer to develop is linked in Jackson’s essay to the career path of Koufax, the specific prefiguring the general.

It may instead be that Koufax’s special case is so compelling that it warps our perceptions of all lefty pitchers. The Dodgers gained so much from their patience as Koufax struggled to unlock his potential. From that, not only do fans learn the lesson that lefties need extra time to reach their peaks, but fans assume teams learned and apply that same lesson.

Possibly the teams did. There may have been a stretch of time when left-handed pitching prospects got a longer leash, an extended opportunity to make things click. Frank Jackson’s casually stated assertion may have been true—for a time. But that time has passed.

Today, there is a ticking clock behind not just lefties, but any pitcher in the majors striving to put it all together. I do not mean age, though that is still true. I mean the limited contractual control their teams have over them.

Nowadays, take six years to build a raw major-league talent to his full power, as the Dodgers did Koufax, and he’ll terrorize the league…for whichever team snaps him up in free agency. Far better, far wiser, to abandon the plan after a couple years and convert him to the bullpen so you’ll get some decent value out of his fastball before you lose him.

That may be why we don’t see lefties, at least lefty starters, taking the long road to peak performance in the current era. The same thought processes would be used with righties, of course, but if they’re faster to get on track, their development won’t be short-circuited as often. In any case, lefties and righties alike would be made to fit the pattern dictated by the approach of free agency.

If you are ever somehow inveigled into a debate where you have to defend the old reserve clause, this may be the best argument in your favor: that it limits the time teams can take to develop players to their fullest and some day could cost us a new Sandy Koufax. If it hasn’t already.

That’s not a conclusion I had anticipated reaching when I started this work. Finding something unexpected, however…yes, I should have anticipated that.

References and Resources

• Frank Jackson, “There’s Always a Reason To Go,” in The Hardball Times Annual 2016
• Baseball-Reference