Jered Weaver’s Favorite Rockpile

One of the things we’re going to try to do more of at FanGraphs going forward is highlight good work from around the web. There’s a lot of good stuff out there, and if we can help more people see the work that’s being done, everyone wins. We’re still going to be doing our normal amount of original content, but we’ll add in some posts here and there that link out to pieces we think are worth reading. This is the first of those posts.

We’ve long known that Jered Weaver got a significant boost from pitching in Anaheim. It’s a park that significantly deflates home runs to right field, and Weaver gives up a ton of fly balls while facing a lot of left-handed hitters. The synergy between his skillset and his home park is one of the best in baseball.

Well, Jeff Sullivan pointed out this morning that there might be more to what’s going on than just a nice alignment of skills and outfield space.

I went through Weaver’s career game logs and identified 16 home starts made in the day time. One was at 3:30pm, and all the others were at or around 1:00pm. I assumed that the weather was always nice, the sun always bright.

That left 68 other home starts, almost all of which started around 7:00pm. The sample sizes here are different, but I think we have enough to make a comparison. When I put the numbers next to each other, my eyes opened wide. The numbers back up the anonymous Mariners player, and then some.

Time	Innings	Batters	ERA	BB%	K%	HR%	Contact%
Day	113	444	1.51	6.5%	28%	1.1%	71%
Night	444	1807	3.00	5.9%	21%	2.4%	79%

The fact that the data lines up with what an opposing hitter noticed instinctively by facing him in a certain situation lends some credence to the belief that this isn’t just small sample noise. It could be, of course, but it could also be that Weaver’s specific arm angle and the position of the rock pile in Anaheim combine to make it very, very hard to see the ball coming out of his hand.

It’s something to keep an eye on going forward, especially if we notice that the Angels suddenly begin to lead the league in afternoon home games.