The John Farrell effect

The Red Sox pitching staff, led by Jon Lester and Clay Buchholz, has made a remarkable recovery so far this year, even with the loss of former ace Josh Beckett. While many conventional baseball minds will try to tell you that the “culture in the clubhouse” has changed so drastically that these players now care more about their performances, sabermetricians don’t buy it.

There must be something concrete to point to in these players’ performances that has caused this sudden turnaround. More than likely, that cause is the presence of manager John Farrell.

Farrell, once a major league pitcher, was hired by the Red Sox as pitching coach in 2007. That 2007 team led the league in pitching WAR and went on the World Series. Based on my observations, the team’s pitching staff drastically improved when Farrell was hired, and got drastically worse when he left after the 2010 season. But is what happened really as cut and dry as it seemed to me?

The Red Sox has 27 pitchers who pitched at least 25 innings 2007 and 2010. If these 27 pitchers, a group that includes four of the five current Red Sox starters, pitched markedly better while they were coached by Farrell than throughout the rest of their careers, then it seems that Farrell really does make pitchers better and explains the current success of the Red Sox.

We’ll compare these pitchers when Farrell was their coach and when he was not based on seven important pitching statistics: ERA, WHIP, FIP, strikeout rate, walk rate, strikeout to walk rate, and home run rate.

In summary, these 27 pitchers performed better under Farrell in six of the seven categories, only being outperformed in walk rate. The splits in ERA and WHIP were especially large, which is surprising because high walk rate is not usually correlated with low WHIP or ERA. This is an interesting discrepancy.

According to PITCHf/x, this group of pitchers threw strikes 50.08 percent of the time while Farrell was their coach, and 59.10 percent of the time when he was not their coach. This explains the high walk rate. But this also has some good results.

While Farrell’s pitchers are throwing fewer strikes, they are causing hitters to swing at balls outside the strike zone five percent more often, and make contact on four percent fewer swings. This is a possible explanation for these pitchers’ good performance despite walking batters.

Another factor involved in the high walk rate is pitch selection. Farrell’s pitchers throw many more off-speed pitches and breaking balls than they did when Farrell was not their coach, and many less fastballs when under Farrell than not under Farrell.

This means that hitters are swinging more at breaking balls and off-speed pitches outside the strike zone, which are difficult pitches to hit. As a result, Farrell’s pitchers induce 12 percent more ground balls than when Farrell is not their coach, and consequently allow 12 percent fewer line drives and fly balls. This explains the improvement in ERA, WHIP, and the other stats that we looked at.

So, in conclusion, pitchers coached by Farrell have been able to be significantly more successful by throwing more breaking balls and off-speed pitches, and throwing more pitches outside the strike zone. This leads to hitters chasing more balls outside the zone, and making less solid contact, resulting in many more ground balls and fewer fly balls and line drives.

Now that John Farrell is back on the Red Sox coaching staff, and the Sox pitchers are playing so well, I think it’s safe to assume that his presence is having a significant positive impact on the pitchers.