There has been a lot of talk about moving Jim Johnson to the rotation in 2012, and I understand the inclination. He's still relatively young (he'll turn 29 next June), he's a fantastic relief pitcher, and starting pitchers are more valuable than relievers. No brainer, right?
I don't think so. In fact, I think the Orioles should leave Jim Johnson in the bullpen where he has excelled.
JJ has made just one major league start, back on July 29, 2006. There is really no information to be gained from one start, so it's best to ignore it (I'm sure JJ would rather forget it happened as well, since he gave up eight earned runs in just three innings). But he was primarily a starter in the minor leagues, with 127 of his 144 minor league appearance being starts.
Way back in 2005, Johnson made twenty-seven starts for the Frederick Keys. While he struck out a very good 9.5 batters per nine innings, his walk rate was higher than it had ever been before at 3.6 BB/9, and he had a very pedestrian WHIP at 1.271. He earned a promotion to Bowie in 2006 where he made twenty-six starts. His ERA jumped up to 4.44 at AA as his walks went down just a bit (3.2 BB/9) and his K rate plummeted (7.2 per nine). That was good enough to be sent to AAA Norfolk for the 2007 season, where as a twenty-four year old he made twenty-five starts, pitching 148 innings. He got his walk rate under control at 2.9 BB/9, but his strikeout rate continued to drop as he struck out only 6.6 batters per nine.
2007 was the last time JJ spent any time in the minors other than injury rehab, as he's been a member of the Orioles bullpen since 2008. In his four seasons in the O's bullpen, JJ has excelled. He still doesn't strike out many batters with an average of just 5.8 K/9 in his big league career, but he's learned not to walk many and he is able to use his sinking fastball to his advantage.
Johnson had a pedestrian minor league career as a starting pitcher and there is little to indicate that he'd be anything more than a Brad Bergesen type in a major league rotation. In 2011, Johnson threw 917 of his 1234 pitches for fastballs. That's about 75%, and he threw it with an average velocity of 95 mph. That's what JJ is built for. If he were to move to the rotation he'd have to use his fastball less often and rely on his other pitches more, and his velocity would likely drop given that he'd need to preserve his energy to pitch at least five innings.
In the article by Steve Melewski that I clipped for this morning's Bird Droppings, he compared Johnson to C.J. Wilson, and that's just not a fair comparison (although in Melewski's defense, he only compared them for innings pitched purposes). As a relief pitcher, Wilson was a strikeout pitcher. He struck out 10.3 batters per nine in 2009, his last year in the bullpen. Since becoming a starter, Wilson's K/9 dropped to 7.5 in 2010 and 8.3 in 2011. Johnson really can't afford for his K rate to drop much more (especially if that goes hand-in-hand with a velocity drop), and that's just what would happen if he joined the rotation.
Jim Johnson can be a mediocre starter or a fantastic reliever. And don't we already have enough mediocre starters?