While Jeremy Bonderman has gotten a lot of praise and hype for his performance this season (and deservedly so) the other right hander in the Tigers rotation has put together a very fine season as well. Jason Johnson had a 3.93 ERA and a 2-2 record going into tonight’s game. And if it weren’t for a horrible outing against Minnesota in which he lasted only a third of an inning, his ERA would be 2.65.

The question is can Johnson keep it up?

Looking at his peripheral stats it isn’t encouraging. Over 34 1/3 innings he only has 12 strikeouts against 11 walks. That anemic strikeout rate is reminsicent of Nate Cornejo in 2003. Looking at those periperhals one would expect Johnson to start getting hit harder unless he can improve his strikeout and walk ratio.

However, thanks to the Hardball Times we can get a little more insight into Johnson’s performance this year. The following is Johnson’s statline from the Hardball Times and the league averages.

Player       RA    ERA   FIP    DER   LD%   G/F   IF/F     K/9   BB/9  HR/9   HR/F
Johnson J. 3.93   3.93  4.39   .702  .090  2.14   .200     3.1    2.8   0.6     9% 
League     4.66   4.26  4.26   .698  .168  1.27   .140     6.1    3.1   1.0    11% 

What jumps out is that Johnson isn’t being hit hard. His line drive percentage is a little more than half of the league average. Line drive are the type of ball in play most highly correlated with hits, so keeping your opponents line drives down increases the fieldability of balls. His ground ball to fly blal ratio is well above the league average. Johnson’s G/F ratio was similarly high last year as he relied on his two-seam fastball and sinker. While ground balls aren’t as fieldable as flyballs, they also typically have less painful consequences if they aren’t fielded. Also working in Johnson’s favor is that is infield fly percentage is 40% higher than the league average. And as this article points out, infield flies are very fieldable.

If Johnson can continue to induce a lot of groundballs and infield flies, as well as continue to prevent line drives, it is reasonable to expect that he can expect to get decent results. Now whether or not he can continue these trends remains to be seen. Last year his ball in play numbers weren’t nearly as favorable. His groundball ratio was 1.55, his line drive percentage was .189 and his IF fly percentage was .082.

Based on his performance tonight, it looks like Johnson’s success is predicated on his ability to keep the ball down. In the early innings, Johnson was leaving the ball up and getting hammered in the process. As he settled in he started keeping the ball down and inducing more ground ball outs.