Jon Lester’s Weak Early-Season Strikeout Rate

Starting pitching is a major weakness for the Boston Red Sox right now. Josh Beckett has been giving up home runs at a prodigious rate and Clay Buchholz has been an unmitigated disaster so far. While first year starters Daniel Bard and Felix Doubront have been above average by FIP (FIP- 86 for both), neither looks good by the more conventional ERA metric (Bard ERA- 118, Doubront ERA- 125). The most disturbing issue with the rotation might be Jon Lester, however.

Lester was expected to be an ace and to match up well against any of the top pitchers in the league. After making his seventh start, he looks more like an average mid-rotation guy. He has an ERA- of 102 and he is only slightly better by FIP- at 91. On his career, he has an ERA- of 80 and a FIP- of 82. This run of average performances is almost entirely the result the result of a dramatic drop in his strikeout rate. From 2009-2011, Jon Lester was one of the top strike out pitchers in the game, his 9.43 K/9 ranking eighth in baseball, just ahead of Justin Verlander. Yes, that Justin Verlander. On his career, he has a rate of 8.30 K/9, but thus far in 2012, he is striking out just 6.00 per nine. Slow starts are nothing new for Lester, but this one is particularly extreme.

April is not Jon Lester’s month. He has a 4.22 April ERA for his career and nearly ever part of his game is weaker in April than in any other month. His FIP and xFIP in April (4.18 FIP and 3.94 xFIP) are well above his career levels (3.66 FIP, 3.73 xFIP) He has a career walk rate in April of 4.06, the second worst of any month. Opponents have a higher SLG, OBP and wOBA against Lester in April than any other month. And of course, his April strike out rate is just 7.74. While there is some precedent for this, his early K/9 rate this year is far worse than any since 2008, when he was in his first full season in the majors.

In 2009, Lester was hit hard in the first month and had the worst April ERA of his career with a dreadful 5.40 in 30 innings. Those struggles continued through May, but starting in June, Lester was one of the best pitchers in baseball, if not the best. As bad has his early results were that season, he struck out 9.90 per nine that April and 10.44 per nine that May. In 2010, he also started slow with a 4.71 ERA, and while control was something of an issue that month, his strike our rate was a fantastic 10.05 K/9. Lester righted the ship quicker that season and was a CY Young candidate by year’s end. 2011 proved to be the exception for Lester, as he was very good in April and struggled in May. His April ERA was an excellent 2.52 and his may ERA was a dreadful 5.50. Oddly enough, he struck out batters at a much higher rate in May (9.75 K/9) than in April (8.06).

While early season rust is something we might expect from Jon Lester, this drop in his strike out rate is extremely unusual. We need to go all the way back to June 2008 to find a period of time where Lester has had a lower K/9 rate. There has been very little change in his average fastball velocity and unlike Clay Buchholz, there doesn’t seem to be any major change in his pitches movements or spin rates. The strangest part of this declining strike out rate is that his individual pitches are still getting very similar whiff rates. Only his cutter has seen a significant drop in whiff rate (down to 12.6% from 14.9% last season) and that is somewhat tempered by the fact that his change up is getting more whiffs (up to 17.9% from 14.9%).

One issue for Lester right now is putting hitters away. In 2012, he has reached two strikes against hitter more often than his career average, but he struck those hitters out less often. In his career, he has a strike out in every 2.31 PA that reaches two strikes, but thus far in 2012 that number is up to every 3.53 PA w/ 2 strikes. That is a very significant gap. Given that his pitches are still able to generate whiffs, I would guess that a combination of bad luck and poor sequencing is responsible for the decline in K’s.

If that is the case, this should be a very fixable problem for Lester. All of his other peripherals remain solid and close to his career levels but he needs those extra strikeouts to be an ace pitcher. If this is just another Jon Lester slow start, he should start racking up the K’s soon. If that doesn’t happen Red Sox fans really do need to worry about him. I think he rebound, but of all his slow starts this is most disturbing one yet.