Should We Worry About Lester?

Jon Lester has been one of the most consistently excellent starting pitchers over the past three seasons, posting ERAs in a narrow range between 3.21 and 3.41. In April of this season, he opened the first month in typical fashion, posting a 2.52 ERA. However, May has been a completely different story as his ERA has shot up to 3.94 after an uncharacteristic 5.50 ERA during the month. Though he made two starts in which he only allowed a run in one and shut out his opponent in the other, he has allowed four runs, five runs twice, and seven runs in his other May starts. Do fantasy owners have any reason to worry?

The first thing that stands out is that he was rather fortunate in May, benefiting from a .257 BABIP and nearly 87% LOB%, which led to an xFIP 0.74 runs above his actual ERA. In May, his luck turned the other way, as his xFIP was actually 1.68 runs below his ERA. Though his April and May performances appear to be night and day when just looking on the surface, his xFIPs of 3.26 and 3.82, respectively, are much closer. These metrics suggest that he did not indeed struggle dramatically in May and actually did not perform too much worse in May than he did in April.

Of course, if a pitcher is not 100% healthy, then his ERA is unlikely to end up anywhere near his xFIP, so what initially appears to simply be bad luck is actually just representative of a pitcher not currently of Major League quality, given his lack of complete health. Though 6.0 shutout innings was sandwiched between his poor starts, his bad streak began in his May 10th start against the Jays. A drop in velocity or loss of the strike zone might be a hint that Lester is in fact hurting. Let’s see if this has actually happened.

First, the good news for Lester owners and Red Sox fans: his velocity has actually increased in his last five starts, though it still remains below last season’s 93.3 mile per hour speed. This is not too much of a surprise, since his strikeout rate was actually much higher in May, so one would not expect velocity to be an issue.

On the other hand, Lester has thrown four of his five pitches for strikes less frequently during his last five starts than his first seven. This would certainly support his increased walk rate in May. When pitchers suffer a sudden loss of control, the first reaction is typically the thought of an elbow injury. We haven’t heard a peep about any possible injury or soreness so it would be difficult to speculate that this was the case.

After looking at the data, I am confident that I now have the answer. It seems as if baseball fans and fantasy owners expect every player to perform exactly as projected in every sample size you look at. ZiPS projected a 3.25 ERA this year for Lester, so fans expect him to post a 3.25 ERA every single month. We stats guys sometimes take flack for ignoring the human element of the game, yet it is the casual fans that ignore this aspect without even realizing it. Baseball is a game of streaks, peaks and valleys, since players are, of course, human beings. Since they are not robots, they will have months of bad luck, months of good luck, months of poor play, and months of strong play. Nobody performs in a straight line.

Sure, Lester’s control has been a bit off in May, but it was over just 29.1 innings (ignoring his first start of the month which was good)! Nothing in his seasonal statistical profile, or even what I parsed out above, truly stands out as a red flag that should give owners any less than the utmost confidence in a pitcher that was likely drafted as a top 10 starter in every league. So settle down Lester worry warts, he will be fine.