New Oriole Gerardo Parra is having a career year. In the first half he hit for a 127 wRC+ despite not registering a wRC+ above 106 in any previous year. Looking underneath the covers reveals that, despite bringing a robust BABIP of .326 into the 2015 season, his first-half BABIP was an even-better .345. This pushed his batting average from a career .274 level (prior to 2015) up to .280 in just 85 games.
A 5.8% jump in career BABIP seemed unsustainable to me. While hitters have more control over their BABIP than pitchers do, it’s still rare for a hitter’s BABIP to reach a new true-talent level during the course of four months. This is an important point to consider when Orioles fans think about what Parra might do for the team through the end of the year. He walks at a below-average rate, so getting base hits is important to his offensive game.
It’s often said that Happiness = Reality - Expectations, and in this case Orioles fans can maximize Happiness by lowering their Expectations for Parra's offensive output going forward. In particular, ZiPS projects him for a .331 BABIP in the second half while Steamer thinks it’ll be closer to .316. For giggles, I did my own study on what fans should expect from Parra in the second half of 2015. The result was closer to the latter than the former.
I looked at players whose career BABIP surged by at least 5% between 2011 and the first half of 2012, 2012 and the first half of 2013, and 2013 and the first half of 2014. (Note that this was their career BABIP, not their BABIP for just one season.) I then looked at the second-half BABIP for those players and calculated the average difference. I did this for batters with at least 20 PA in each half. This is not a huge sample, so the results aren’t perfect, but it illustrates the concept of regression to the mean well.
Here’s an example. Through 2011, Nelson Cruz had a career BABIP of .303. In the first half of 2012 he registered a BABIP of .335, a 10.5% increase. In the second half of 2012, his BABIP dipped to .265. That’s what regression to the mean looks like. Not everyone experiences it; for example, Torii Hunter's BABIP spiked 7.6% in the first half of 2012 and then rose by a whopping 36% in the second half.
But he and fellow surgers Tyler Colvin, Andy Dirks, and Jason Heyward were the exceptions to the rule. The remaining 13 BABIP surgers saw their second-half BABIP drop. All in all, the average first-half-to-second-half drop for these surgers was 14.5%. That’s quite a lot! It would take Parra’s BABIP from .345 to .294 and really put a dent in his batting average.
I repeated the study for two more seasons. In 2013, players whose BABIP surged in the first half saw it drop by about 6% in the second half. That’s not so bad. But in 2014, surgers experienced a BABIP drop of 11.3%.
Put it all together, and the data show an average second-half drop of 10.6%. This shows what fans should expect from Parra's second half. A BABIP of .309 is far more likely than a repeat of his .345 first-half BABIP.
What does a .309 BABIP look like? It looks like Corey Hart and James Loney. Prior to 2015, these are the two players with at least 700 balls in play who have a BABIP of .309. If you widen the scope to BABIPs between .308 and .310, you also get Lyle Overbay, Torii Hunter, Rafael Furcal, Grady Sizemore, and Brian Roberts. If you expand the scope to career BABIPs between .307 and .311, you add in Melky Cabrera, Martin Prado, Alex Rios, and Asdrubal Cabrera. One step wider and you get Jose Reyes, David DeJesus, and Omar Infante.
These are all good major-league players. There’s a lot of speed in there and some above-average contact ability, both of which Parra has shown in his career so far. The bad news is … well, there’s no real bad news here unless fans thought Parra would repeat his first-half slash line of .309/.344/.496. The evidence shows that’s just not likely.
But for what the Orioles gave up and where they are, Parra just needs to be an offensive upgrade. And he will be that. Orioles left fielders hit .235/.299/.378 in the first half. The resulting .297 wOBA gave the Orioles the 7th-worst production in the game at that position. Parra should ensure that the Orioles eke a bit higher in those rankings before the season's over.