What’s eating Edwin “Gilbert Grape” Jackson?

In the recent off-season, the Cubs signed Edwin Jackson, hoping he could help stabilize their needs at the middle-end of the rotation. While Jackson has bounced around to many a team over the course of his career, he can certainly be serviceable, as he posted (pitching) WARP over 2.0 twice – 2009 with Detroit and 2011 with the White Sox.

Though it is a fairly small sample size, Jackson has now roughly pitched 1/4 (7) of the projected starts (30) this season. In those 7 starts, Jackson has averaged just over 5 1/3 innings per outing. Though he has never recorded a season long ERA worth writing home about – exluding small sample sizes, his best mark came in 2009 when he posted a 3.62 in 33 games with Detroit – his 6.39 average this season is quite alarming.

What could be the reason for such a jump this season?

My first instinct was to look at fly-ball rate and the park factor. According to ESPN, Wrigley Field has been home to the most hitter friendly contests this season. But with a closer look, we can eliminate that as the  factor, as in his four home starts, he has yielded just one home run. On the flip side, batters hold a .352 average against him at Wrigley, opposed to just .188 on the road.

Still, Jackson has improved his ground ball rate from 42% last season to 48% this season. This could definitely be a reason why his HR/9 last season was 1.1, compared to just 0.5 this season. It’s comforting to see that gb% increase when you play in such a hitters’ park, especially one so influenced by winds blowing out from home plate.

So, if the long ball isn’t the problem, then it must be…?

Well, I think the main reasons for the jump in ERA comes down to BABIP and his (lack-of) control.

Jackson has already handed out 18 free passes this season, which isn’t helped by the fact that his opponents are hitting .353 against him on batted balls in play. According to Jonah Keri, the league average is somewhere around .290 for BABIP, so we should see that number decrease over the course of the season.

The decrease can’t come soon enough, as a team that is 16th in the majors in ERA (3.95) will have a hard time winning games if they continue to remain towards the bottom of the league (24th -113) in runs scored.

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