Do you recall this article from Sabernomics which showed the top over- and under- OPS performances based on prOPS as May 15 of this season? PrOPS is based on a model which predicts the "expected" OPS based on variables such as they types of batted balls struck by the batter. In the words of its creator, J.C. Bradbury:
Players who are over- or under-performing their PrOPS are more likely to decline or improve than players whose performances are in-line with their OPS. PrOPS does not remove all aspects of luck, it just highlights one common area where random bounces on the field can distort outcome-based metrics.
The noteworthy point from this early season article is that Hunter Pence was the unluckiest hitter--in terms of the difference between actual OPS and PrOPS--in the majors on May 15. Given that the Astros were mired in a hitting slump of epic proportions, this was a small bit of good news for saber-oriented Astros' fans, since it suggested that Pence's OPS was due for an improvement. Unfortunately, I don't know of any source for ready access to current PrOPS stats. However, we can do a little retrospective, and see how well PrOPS forecasted reversion to the mean for Pence.
Below I've shown the May 15 OPS, May 15 PrOPS, and second half of the season OPS for Hunter Pence.
May 15 OPS .705
May 15 PrOPS .927
Second Half OPS .856
Pence's OPS has tailed off in recent days. A week or so ago, Pence's second half OPS stood almost equal to his May 15 PrOPS. Regardless, the PrOPS correctly pointed to a solid improvement in Hunter's OPS over the second half of the season.
The No. 2 unluckiest hitter on May 15, based on PrOPS, was Skip Schumaker. Let's look at how his second half turned out.
May 15 OPS .589
May 15 PrOPS .800
Second Half OPS .761
While we're at it, let's look back at the luckiest OPS for players on May 15, again based on PrOPS. Setting aside Justin Morneau who suffered a head injury, the top overperformers were Jayson Werth, Colby Rasmus, and Carl Crawford.
May 15 OPS .1.089
May 15 PrOPS .836
Second Half OPS .881
May 15 OPS .950
May 15 PrOPS .795
Second Half OPS .833
May 15 OPS .868
May 15 PrOPS .710
Second Half OPS .768
Overall, PrOPS did a fairly good job of pointing out the potential for these early season offensive performers to undergo a fall off in their OPS later in the season. One of Astros' players who was in the top 20 of OPS underperformance, based on PrOPS on May 15 was Carlos Lee.
May 15 OPS 514
May 15 PrOPS .636
Second Half OPS .763
Had you forgot how low Carlos Lee's OPS was early in the season? Lee's rebound in the 2d half exceeded his PrOPS early in the season, but it still is lower than one would like. It would be interesting to know whether Lee's PrOPS for the second half of the season is higher than his actual second half OPS.You may recall this post from May, which pointed out that the Astros' team OPS was the unluckiest in baseball on May 15. Expecting PrOPS to predict rebounds by teams is subject to some distortion, since the teams can and do change their player composition during the season. The Astros are a good example of that tendency. But we can still look at how good an indicator PrOPS was for the Astros.
May 15 OPS 599
May 15 PrOPS .720
Second Half OPS .702
Sure, you can say that the Astros had nowhere to go but up on May 15. But I will rack this up as a good prediction by PrOPS on May 15. PrOPS told us that the top overperforming teams on May 15 were the Twins, Nationals, Giants, and Rays. Among those teams, only the Twins continued to maintain the team OPS level in the second half. PrOPS was correct in predicting a second half OPS decline for the Nats, Giants, and Rays.
Nothing all that surprising here. But I think this comparison shows that PrOPS is a decent indicator that players or teams are likely to a rebound or decline in future OPS performance.