In July of 2011, Jon Lester was placed on the disabled list with a strain of his latissimus dorsi. That's located on the back portion of the shoulder, all the way down to the hip, and a strain can cause decreases in velocity as well as loss of command. (Or, if you're Jake Peavy, it can detach entirely from your shoulder and cause you to miss significant time.) He returned after 19 days and 14 games missed, and appeared to be mostly intact.
Since the injury, though, he's been inconsistent, oftentimes missing his spots and issuing far more walks than in the past. Prior to the strain, Lester had thrown 114 innings in 2011. He had struck out 8.7 batters per nine while walking 3.1 per nine, nearly three times as many punch outs as free passes. In the 101 frames he's pitched since -- stretching from late July 2011 through Monday against the Twins -- Lester has struck out just 7.8 per nine, while walking 4.3 per nine. That's a significant jump, and the amount of time it encompasses is quickly approaching the point of stabilization.
Walk and strikeout rates take time to have meaning. Russell Carlton, formerly of Baseball Prospectus but now with the Cleveland Indians front office, has studied just how much time it takes. After 150 batters faced, you can start to trust a pitcher's strikeout numbers. It takes much longer for walk rate, at 550 batters faced, and about 500 batters to get a feel for the validity of a pitcher's strikeout-to-walk ratio. This is why it's tough to figure out relief pitchers, by the way, as it takes over 100 innings of work before you start to see something akin to realism in their numbers, and that can take more than a season to compile.
Lester has faced 426 batters since returning from the disabled list in July of 2011. That's a few starts away from his recent K/BB ratio becoming more than just a rough stretch, and that's not good news for a Red Sox team that needs its rotation to be in order while the lineup and bullpen suffer through injuries. What's caused this change?
It's unlikely that the latissimus dorsi strain is still problematic for Lester, in the sense that it's still causing him pain and discomfort. However, it's entirely possible that, in order to compensate for the strain, Lester developed some bad habits in his mechanics that haven't been ironed out yet.
"Believe it or not, early elbow problems cause control issues while shoulder problems cause velocity changes," says athletic trainer and baseball writer Corey Dawkins. "Maybe he's sore and not telling anyone, but for the lat to be the direct cause of his control issues is unlikely, unless he is purposely (or subconsciously) changing something."
Dawkins believes it's unlikely Lester would still have this problem long-term, but there are plenty of reasons to think that it might be the case. Lester has not only issued more walks, but his command has suffered and kept him from putting hitters away, even when ahead in the count. He alternately looks untouchable and unable to get anyone out, not just from start-to-start, but occasionally from inning-to-inning. Someone who was a legitimate Cy Young contender just 12 months ago shouldn't be going through this unless something is amiss, especially when their stuff isn't diminished in any way.
Sam Miller wrote about Lester's 50-pitch inning against the Texas Rangers the other night, one of the moments where he didn't look much like Jon Lester. His mechanics are completely different depending on when you saw him, with his leg kick changing, and his body and arm out-of-sync, the latter whipping the pitch rather than moving along with his trunk. Doug Thorburn, also of Prospectus, goes into more detail about these two pitches:
The "early" pitch is well-timed with solid balance and a glove that stays in front of the body, and Lester paints the target. The "late" pitch lacked the balance of the early one, with his head trailing his center-of-mass into foot strike. Meanwhile, the glove-arm flops lazily to his side on his follow-through. But the main symptom of the missed target is late initiation of trunk rotation, and his arm fails to catch up to the body, this despite the fact that his stride timing looks pretty similar.
I thought that Lester was really unlucky at the start of the second inning, barely missing his targets and watching batters hit some quality pitches, with no help from the defense. But Lester was exhausted by the end of the second, having thrown something like 49 pitches (an insane count)-the 12-pitch foul-a-thon with Beltre was just torture to watch-and the "late" GIF does a great job of exemplifying how mechanics can suffer as a pitcher fatigues.
(Be sure to read Sam Miller's account of the game, as there's more to it than these quotes; painful as it might be for a Red Sox fan to relive that game, Miller is his typical excellent self.) The cause of these changes was in part fatigue, but Lester has set himself up for plenty of long, tortuous innings in his last 100-plus, even if they didn't result in 50 pitches every time. There would be less reason to worry if this were the first time things went down like this.
Whatever the issue is -- focus, the need for a slight mechanical tweak to bring him back to where he was -- Lester and the Red Sox need to get it in order for the lefty to be at his most productive. The Red Sox have enough uncertainty on the roster without seeing one of their stars fail to do what he's capable of every five days.