ERA aside, Lester Still Strong

With Boston's season quite possibly on the line, Jon Lester takes the mound tonight against the Orioles. The lefty has been drubbed for 17 runs in 25.2 innings pitched in September, contributing to a starting pitching collapse that has erased what was an 8.5 game lead over the Rays in the Wild Card race to begin the month.

Further stoking Sox fans' fears, Lester is pitching on three days' rest. Starters throwing on short rest tend to get rocked: according to Baseball-Reference, starters' opponent on-base-plus slugging percentage was 13 percent higher on three days' rest than in other situations in 2010, and 27 percent higher in 2011.

But, rather than painting an apocalyptic picture of a tired Lester getting rocked against the O's, I'd like to point out a few reasons why he's still Boston's best hope of avoiding what Nate Silver suggests could be the worst September swoon of all time.

- Lester might have an ERA nearing six this September, but his fielding-independent numbers are still strong. His xFIP, an ERA estimator based on strikeouts, walks and a normalized home run per fly ball rate, is 3.75 this month. Lester hasn't been ace-like, but he shouldn't be mentioned in the same breath as John Lackey, Tim Wakefield, Kyle Weiland, Erik Bedard and Andrew Miller, whose combined xFIP in September is 5.47 (Josh Beckett also has a strong xFIP of 2.96).

- Shallow bloop hits in the outfield and bleeders in the infield have caused much of Lester's September woes. Here's his opponent hit chart for the month:

Lester's in-play average (including homers) is .403 in September, compared to .301 from April-August and the .320 league average. Whereas Lester got roughed up when he missed high and down the middle through August, he's giving up those seeing-eye hits all over the zone in September:

Lester's in-play average by pitch location, April-August 2011                  Lester's in-play average by pitch location, September 2011 - It's not pitch location, either. Virtually nothing has changed in terms of where Lester is throwing the ball:

Lester's vertical pitch location

April-August: 30% thrown up, 33% middle, 37% down

September: 29% up, 34% middle, 37% down

Lester's horizontal pitch location

April-August: 30% inside, 21% middle, 49% outside

September: 31% inside, 23% middle, 46% outside

- Lester's velocity isn't down. He's still sitting 92-93 mph with his fastball, maxing out at 96, and tossing his cutter around 88-89 mph.

- The "pitching on three days' rest" narrative is a bit misleading, as Lester threw just 55 pitchers in his September 24 start against the Yankees. For a guy who topped 200 innings three straight years prior to 2011 and has averaged about 105 pitches per start this season, fatigue might not be such a big issue.