The “Trop Effect” on Flyballs

By Robbie Knopf

We see it happen every few games. There’s a flyball and the visiting outfielder completely loses the ball in the roof and lets it drop. How much does it benefit the Rays?

Let’s look at the BAbip on flyballs for the 2011 Rays, their opponents, and the MLB average. In terms of straight BAbip, the MLB in average in 2011 was .137. The Rays were at .127 while their opponents were at .124. 16.5% of the Rays’ flyballs ended up as extra-base hits, just about the MLB average, compared to 16.3% for their opponents. And 78.9% of the Rays’ flyball hits were extra-base hits compared to 81.4% against them and the 77.5% league average. The Rays and especially their opponents have traded some flyball hits to hit for more power than average. Because of that we would expect their overall rate of singles will be below-average. Indeed, it is. 4.4% of the Rays flyballs ended up as singles, a bit below the 4.8% average, but well above the 3.5% mark of their opponents. That’s even more interesting when we look at the overall single rates for the Rays, their opponents, and the average. The Rays are at 13.7%, their opposition at 13.5%, and the league average is at 15.3%. We see that the Rays are a more noticeable margin off from the league average overall, not just in terms of magnitude (1.6% compared to .4%), but also in terms of percentage of the total (10.5% to 8.3%). But that’s nothing compared to the difference between the Rays and their opponents. The difference is .9% for flyballs compared to just .2% and 20.5% of the total compared to just 1.5%. The Rays are a team that hits for solid power. They posted a .158 ISO in 2011 compared to the .144 MLB average. Yet strangely for flyballs they hit considerably more singles than their opponents and were closer to the league average.

How much of that is the Trop itself? Hard to tell. Maybe the Rays just hit a bunch of bloop singles- but then their BAbip would have been higher on flyballs. An above-average percentage of their flyball hits were extra-base hits. They were not hitting weak flyballs. Is this all from the Trop? Definitely not. But part of it definitely is. In 2011, the Rays got 13 more flyball singles than their opponents despite 59 less flyballs. We’ve seen how pop-ups lost in the Trop roof have helped the Rays win games. There’s a lot of things not to like about the Trop. But the roof is a clear home-field advantage for the Rays.