Originally written on Fangraphs  |  Last updated 11/18/14

From 2008 to 2010, there were only six pitchers in baseball better than Jon Lester, and you can probably identify them all by first name — Roy, Cliff, Tim, Zack, CC and Justin. Last year however, was a different story. Lester was still one of the top 30 pitchers in the game, but he was ensconced safely outside of the top 10. While many expected a rebound, or at least for Lester to plateau in 2012, he has continued his descent, with the exclamation point coming yesterday, when he allowed 11 runs in four innings to the Blue Jays.

As we noted last week with Jonathan Sanchez, part of Lester’s trouble may stem from the fact that while his fastball velocity is declining, his changeup velocity is increasing. The changeup hasn’t been a problem for Lester this season, but his fastball certainly has. Lester has not even lost a mile and a half on his four-seamer, and it is still the ninth-fastest four-seamer among left-handed starters. But that sentence is a bit of a tip off, isn’t it? Two seasons ago, that sentence would have read “tied for 11th-fastest in the game.” Now, it needs qualifiers. Also, it is getting hit hard — he is allowing a .397 wOBA on his fastball this season.

Still, that’s not what is most troubling. In 2010, when Lester posted a 3.13 FIP, he allowed a .396 wOBA on his fastball, so clearly he can be effective without a dominating fastball. But what Lester does need to be effective are the pitches that break — his cutter, curveball and sinker — and right now, they are not. His cutter, in particular, has been a mystery. For starters, he is either throwing it less frequently or he has been throwing it in a way that makes it harder to identify as a cutter. That can sometimes be attributable to a computer or user error or change in how pitches are identified, but if it isn’t, it’s a big issue for Lester moving forward. Over the last three seasons, the cutter had been Lester’s bread and butter, and had been one of the most effective cutters in the game. From ’09-’11, he threw it 20.5 percent of the time. This year, that has dipped to 11.5%. Hitters are still having trouble squaring up the pitch, but they’re not missing it with the frequency they have in the past — his SwStr% on his cutter is four percent lower than it has been the past three seasons.

His curveball and sinker have not been much better. First, let’s look at his curveball:

Year PA wOBA 2007 26 0.103 2008 123 0.238 2009 105 0.189 2010 135 0.18 2011 95 0.254 2012 53 0.371 Total 537 0.223

Now, what we’re looking at here needs to be taken with a grain of salt. Because only 53 of the batters he has faced this year have seen a curveball as the final pitch in said plate appearance, there is room for noise in these numbers. But it bears watching, since Lester’s wOBA allowed on curveballs is currently is almost 150 points above his career norm. In addition, perhaps it should tell us something that he is featuring it that much less frequently at the end of plate appearances the past two years.

His sinker has stabilized a bit better, but the results there aren’t promising either:

Year PA wOBA 2010 109 0.325 2011 126 0.353 2012 150 0.373 Total 385 0.353

Lester is throwing his sinker more than ever before even though it is getting harder than ever before. And unlike in 2010, when he had a respectable 8.7 SwStr% on the pitch, he is only getting swings and misses on 4.0% of his sinkers this season. Which would be fine if he was generating weak contact, as sinkers are not necessarily designed to be a swing and miss pitch, but he’s not. He’s getting hit hard, and what’s worse, he’s getting his sinker hit into the air — a career-worst 22.8% of the time.

Add it all up, and Lester is throwing four of his five pitches below the standards to which he is accustomed. When things like that happen, you end up with a second straight season of pronounced platoon splits. When things like that happen, you end up with a career-worst 23.3 LD%. When things like that happen, you post the worst HR/FB of your career. And yet, is Lester really doing that poorly? He’s still been worth close to two wins, and if you look at his minus numbers, he’s still been a better-than-league-average pitcher. His K% is down, but so is his BB%, and his K/BB numbers are in line with his last two seasons. His BABIP is up a lot this season, and that could be because his pitches have lost some of their mojo. It could also be just bad luck. Certainly, starts like yesterday’s don’t come around too often, and when they do, the opposing team doesn’t always cash in to the degree the Blue Jays did. On Wednesday, Justin Masterson had a very similar start in terms of baserunners allowed and innings pitched — 14 in 4 1/3 innings against Tampa — but the Rays only cashed in four of them.

It is clear that Jon Lester has slipped from ace status, but how far is still up for debate. His pitches have been far less effective, and his platoon split is troubling, especially since the overwhelming majority of the batters he faces are right-handed. Yet, as recently as last month, he had posted a season-best monthly FIP of 2.92. His E-F number is third-worst in the game at the moment and his 3.80 xFIP places 39th out of 100 qualified pitchers. Interest certainly hasn’t dampened on him either, as the Braves have recently inquired about his availability.

Lester’s struggles will continue to be magnified in Boston because, number one it’s Boston, and number two the Red Sox — thanks to the fluctuation of both health and effectiveness of every other member of its starting rotation — need him now more than ever. If he is able to turn things around, then his last three starts — in which he has allowed 22 runs in 12 1/3 innings — will become a blip on the radar screen, much like when he allowed 15 runs in 16 innings in his first three starts of 2010. If he isn’t, we will remember this past weekend as the time when we stopped referring to him in the same discussions with guys like CC, Justin, Cliff and Roy.

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