by Eno Sarris // 

Brad Penny once pitched in the American League, and the results were less than stellar. While it’s tempting to say his return to the harder league will go as poorly, there’s little black and white here. Let’s unpack what went so poorly for Penny in Boston, why he returned to grace in the National League, and what that might mean for him now that he’s a Detroit Tiger.

Penny had a 5.61 ERA in Boston and a 2.59 ERA in San Francisco in 2009 – and yet his performances were much closer to similar than would first appear in looking at ERA alone. In Boston, he struck out 2.12 batters for every one walk, and in San Francisco he struck out 2.22 batters per walk. He had an FIP (Fielding-Independent Pitching – a stat that runs on a similar scale to ERA, while stripping out defense and luck and focusing on factors the pitcher can control) of 4.49 in Boston; his FIP in San Francisco was a similar 4.35. The big difference was that Penny yielded a very lucky .211 batting average on balls in play while wearing black and orange, pushing his ERA much lower.

Oh, there was one difference worth mentioning. Penny had a 40.8% groundball rate in Boston, and a 53.8% number in San Francisco. As Penny’s strikeouts have tumbled over his career, his groundball rate has climbed – his three best years by groundballs have come in his last four years, for example. That went away in a short stint in Boston, but he re-found his ability to get grounders in San Francisco.

And he continued to coax ground balls in St. Louis last year, before a lat injury cut his season short. In those nine Cardinals starts, he managed a 52.8% groundball rate that would fit in with his recent work in the category. He did refine his cutter with Dave Duncan, and also threw far fewer four-seam fastballs than he had in the past. But let’s not count on the Duncan bounce lasting beyond the friendly confines of Busch Stadium; the Tigers’ curious roster could hurt his new team’s ability to turn grounders into outs as is.

Looking at some comparable American League pitchers given Penny’s statistical benchmarks, we find Fausto Carmona (5.31 K/9, 3.08 BB/9, 55.6% GB), Trevor Cahill (5.4 K/9, 2.88 BB/9, 56% GB) and possibly Rick Porcello (4.65 K/9, 2.1 BB/9, 50.3% GB). Those ERAs ranged from 4.92 (Porcello) to 2.97 (Cahill), but use FIP instead, and the range narrows to 4.11 to 4.31. The average FIP in baseball for qualified pitchers last year was 4.08.

The injury concerns are there, even if Penny lost most of the year to a non-arm injury. Given his mix of passable strikeout-to-walk ratios and good groundball rates, Penny should be able to approximate an average major league starter for the Tigers. From the list above, you can see that he might even luck into a stronger fantasy season. But his recent history also suggests that there’s no way you can depend on him. Put him in the leave-a-penny-take-a-penny tray on draft day in standard 12-team mixed leagues, and use him if/when you need him during the season.