Much has been written about Nate Cornejo’s “success” this season despite his unfathomably low strike out rate of 1.6 K/9 IP. Baseball Prospectus did a piece in early June (when Cornejo was really humming along with a sub 3.00 ERA). It showed that with runners on base, only 17% of balls in play resulted in hits. This was dramatic because the Tigers team was allowing hits on 27.1% of balls in play at the time. If you believe the theory that pitchers don’t really effect the outcome of balls that are hit in play, then you believe Nate was incredibly lucky.

Since the article was written on June 1, Cornejo has had two good outings, and a bunch of bad ones. Looking at the rate at which balls in play become hits, it has risen dramatically.

So what does this tell us? Basically that Nate was pretty lucky early in the season, and that he’s been pretty unlucky as of late. Considering that for the season, the Tigers have allowed hits on 27.9% of balls in play, it looks like for the season Cornejo has actually been a little bit unlucky. Based on the team rate, you would expect Cornejo to have allowed 100 hits on the season. That’s a difference of 10 hits over 17 games, or about .6 hits per game.

Because Cornejo’s K rate is so low, along with a low walk rate and average home run rate, 86.5% of the batters he faces put the ball in play. The league average is 72.5%. Why is this important? Because so few of his outs are strike outs, Cornejo is very reliant on his defense to help him out. When he’s “pitching unlucky” he’s really getting burned. In June and July when Nate was “pitching unlucky” he gave up 59 hits. With the same unlucky defensive efficiency, a pitcher who allows balls in play at the average rate would have allowed 48 hits. Over those 7 games that’s a 1.6 hit per game difference.

This also leads into a brief discussion of pitching efficiency. Bob Cluck’s argument in favor of Nate’s low strike rate is that Cornejo’s pitching is more efficient than a traditional player. While in theory, Cornejo maybe able to get a given batter out with fewer pitches by inducing players to put the ball in play, he’ll ultimately end up facing more batters as more reach base. Nate is averagig 3.53 pitches per plate appearance, and 15.4 pitches per inning. I don’t know league averages for these stats, but they don’t feel extremely efficient to me. And, it could be argued that any improvement over league averages could be attributable to Cornejo’s lower than average walk rate.

I’m not sure if this answered any questions, but it was definitely interesting to do. I’d like to give a little plug to Twins Geek who inspired this analysis with a couple of articles (this one, and this one) that he did a couple weeks ago. Plus, it’s a really great site.