After a not very good 2009 and a similarly not very good 2010, David Hernandez has finally lost his spot in the starting rotation. 143 innings isn’t an especially huge sample size, but thus far Hernandez hasn’t been able to translate his minor league strike-out totals to the majors (career 6.0 K/9). His control has gone from bad (4.1 BB/9 last season) to worse (6.o BB/9 this season), and though he’s cut his home run rates in half, it’s just gone from fluky high to fluky low – David is still an extreme flyball pitcher that will struggle with the longball.
I looked at what a move to the pen could mean for Hernandez previously, and concluded that it wouldn’t be a magic bullet for him. He doesn’t have the most massive of platoon splits to take advantage of, though lefties (6.11 xFIP^) are doing better against him than righties (5.35 xFIP). His fastball has some giddy-up and he might pick up a little more speed, but it doesn’t miss a lot of bats. Going to the pen would allow him to scrap the change-up, more or less, but he doesn’t throw it that often anyway. Even just looking at his stats for the first plate appearance against him in a game, his K/BB is still only at 1.8. I think Hernandez can be a decent reliever, but expecting him to go from a 5.40 ERA guy to a 3.40 ERA guy is just not realistic. It doesn’t mean it won’t/can’t happen, but David just honestly isn’t that good of a pitcher and unless he drastically improves his control that isn’t likely to change.
And before anyone brings up Jason Berken (though I’m a big fan), his xFIP went from 5.10 as a starter to 4.31 as a reliever – completely in line with the improvement one would expect. I’m sure there are other guys you can throw out that were much better relievers than one would have thought based on their starting stats but (1) of course that’ll happen sometimes, partially due to luck, and (2) beyond his velocity (which isn’t really serving him that well as a starter), there isn’t really any reason to believe that Hernandez will be a special case.
Taking the vacated rotation spot will likely be Chris Tillman, joining the roster from Triple-A. Tillman’s been pretty good in Norfolk and threw a no-hitter a little while ago. His control has been superb at 1.9 BB/9, which leads me to think that a lot of his improvement in that area last year has stuck. Walking batters wasn’t a really big issue for him in the majors in 2009 (3.3 BB/9), but every little bit helps.
Tillman’s not blowing batters away though, with a 7.3 K/9 that’s the lowest of his minor league career. He K’ed over a batter an inning last year in Triple-A, but that rate fell to just 5.4 K/9 in Baltimore. It’s certainly possible that he’s working on some things – like a cutter – that are contributing to the lower strike-out rate, and it’s important that he be able to get it up to at least average (~7 per nine) in the majors eventually.
Tillman’s biggest problem from last season – the home runs (and more directly, the flyballs) – doesn’t appear to have changed. He got groundballs 37% of the time in the big leagues last year, and that’s down to just 33% in Triple-A now. It was 39% prior to his call up in 2009, so that’s a step back instead of forward. I’ve said it before and I’ll say it again; if you give up a lot of flyballs then some of them are going to find the seats.
Before the season, all of the (reasonable) projection systems called for a strike-out rate in the 6’s, a walk rate in the 3’s, a bunch of home runs, and an ERA (well, FIP^) in the 4.75 to 5.00 range. That would make Tillman a below average but above replacement level pitcher. If his improved control transfer then that will be great, but missing bats and locating down in the strike-zone more are going to be crucial to his success.