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Rick Porcello, BABIP, and infield defense: Why Rick Porcello's numbers may have nothing to do with Rick Porcello

Many people believe that Rick Porcello will benefit from an improved infield defense in 2014, but do his career numbers suggest the same?

David Manning-USA TODAY Sports

Rick Porcello has been tabbed as a potential breakout starter for the Tigers for nearly as many years as he has been a member of their rotation. Rotowire had fantasy baseball players on the lookout for him in 2011. Baseball Prospectus tabbed him as one of 14 breakout players in 2012. ESPN Insider and Fangraphs (via ESPN Insider, oddly) took their shots at Porcello breaking out in 2013. This year, MLive and ESPN Insider are back at it again.

Writing an article about why Porcello will break out has become the new "best shape of his life" story, while writing an article about why Porcello will not breakout is (a) a bit too baseball hipster-ish for my liking, and (b) kind of mean, considering he made some significant leaps in production in 2013. Instead, let's look at why it may have nothing to do with Porcello and everything to do with the four individuals right behind him.

Rick Porcello faced 736 batters in 177 innings pitched last season. Of those, 549 put the ball in play, with 300 hitting ground balls. This figure ranked second on the team, behind Doug Fister's 359. Opposing batters reached base 26% of the time when hitting a ground ball off Porcello. Once again, he ranked second to Fister in this regard, as opposing hitters hit .287 off ground balls from the now-Nationals starter. Both ranked far above the league average of .245.

Another way to describe this is to use the statistic BABIP, or batting average on balls in play. To cut down on extraneous wording, I'm going to use the acronym gBABIP for the rest of the post to indicate BABIP splits on ground balls. Porcello allowed a .260 gBABIP in 2013, while Fister's gBABIP was .287. The American League average was just .245, a figure that was well above the .238 gBABIP that AL pitchers have averaged in three of the last four seasons.

Most of the blame for Porcello's and Fister's high gBABIP figures fell upon the Tigers' porous infield defense. As a team, the Tigers allowed a .270 gBABIP, by far the worst mark in the American League. This was the fourth consecutive year that the Tigers allowed a gBABIP above league average, and they have not been particularly close in any of those seasons. The last time the Tigers had an above average infield defense was 2009.

Year Tigers League Difference
2013 .270 .245 +.025
2012 .254 .238 +.014
2011 .255 .238 +.017
2010 .244 .231 +.013
2009 .232 .238 -.006

Conspiracy theorists already know where I am going with this: Porcello's 2009 season is considered by many to be the best of his young career. It is the only time he has allowed an ERA under 4.00 and the only time his ERA has outperformed his FIP (which has improved in each of his five seasons). Porcello has a 52.8% career ground ball rate and has been above 50% in each season. Despite tinkering with his pitching repertoire, he has shown remarkable consistency in his ability to generate ground balls in his five major league seasons. He ranked second in the AL in both ground ball rate and ground ball-to-fly ball ratio in 2013, and has consistently ranked among the league leaders during his career.

This does not tell the whole story, though. Tigers pitchers have had gBABIP rates well above league average, but what about Porcello himself?

Year Porcello League Difference
2013 .260 .245 +.015
2012 .242 .238 +.004
2011 .276 .238 +.038
2010 .245 .231 +.014
2009 .206 .238 -.032

As one might expect, Porcello has been a victim of some poor infield defenses for most of his career. The small difference between Porcello's gBABIP and the league rate in 2012 is interesting, but not very informative. His poor 2012 numbers -- namely, his 0.68 difference between his ERA and FIP -- is largely due to a 24.2% line drive rate resulting in a career high .344 overall BABIP. His extremely low gBABIP in 2009 is not predictive of what is to come in 2014, but I would wager that Porcello's gBABIP approaches league average.

Unfortunately, we cannot separate Porcello's gBABIP splits by month to determine if Jose Iglesias had any impact on his numbers in 2013. However, judging by the team's overall BABIP splits, it may be too early to tell if the defensive wunderkind will shore up the Tigers' porous D. Tigers pitchers allowed a .306 BABIP in August and a .324 BABIP in September, rates that would average just above their .308 mark for the entire year.

However, Iglesias is not the only upgrade the Tigers have made to their infield defense in the past year. Miguel Cabrera's career -2.2 UZR/150 at first base is much better than Prince Fielder's -5.6 UZR/150, and the five-inch height difference between the two may provide additional benefit not reflected in advanced defensive metrics. Across the diamond, Nick Castellanos is likely to be better than the -26.5 UZR that Cabrera provided at third base over the past two seasons. Ian Kinsler and Omar Infante look to be equally sturdy with the glove at second base, though Kinsler's career 51 defensive runs saved dwarfs Infante's two (Kinsler has a 3,000 inning advantage).

There are a lot of factors that will determine how Porcello's 2014 season shakes out, but an improved infield defense has shown -- in one season, at least -- that it can positively impact his numbers. Combine the upgrades to the Tigers' 2014 defense and Porcello's personal improvements since his rookie season, and he may finally be poised for that breakout season everyone has been waiting for.