Jake Peavy Lands in Boston

After weeks of speculation, Jake Peavy has finally been traded. He departs the windy city for the land of clam chowder and from a team going nowhere to one right in the thick of the AL East race. Or more simply, he is is changing the color of his sox from white to red. My initial thought is that this move produces a nice boost to his fantasy value. But let’s dive into the numbers and find out if this is actually the case.

Since Peavy isn’t switching leagues, our analysis is a bit easier. We only need to compare ballparks, team offenses and defensive support, while ignoring any effects from crossing leagues. So let’s check out the relevant numbers from our park factors (remember they are all halved to account for the fact that players only play have their games at home).

The first thing we notice is that looking at overall run factors, both parks favor hitting and inflate offense at a very similar rate. But the way offense is inflated is different. Fenway Park, with its quirky dimensions and Green Monster, significantly increases doubles. It barely has an effect on singles and triples, but even its neutral conditions are a better environment for hitters than U.S. Cellular Field.

Where The Cell makes up ground is in the home run department. Last season, the park ranked second in baseball in home run park factor. So while hitters at Fenway are busy banging doubles off the Green Monster, hitters at The Cell are busy knocking balls out of the park.

Aside from the effect it has after the hitter puts the ball in play, there are differences when the hitter does not. Both strikeouts and walks increase at The Cell, while Fenway is pretty much neutral.

As a fly ball pitcher, home runs can be problematic for Peavy. His HR/FB rate this season sits at a robust 13%, the second highest mark of his career. However, his home/away HR/FB splits are nearly identical, so we cannot necessarily blame the park this time. That said, getting out of a less homer friendly park has to be a good thing. Of course, he might see an increase in BABIP given Fenway’s propensity to inflate all types of hits that stay in the park. But a double is certainly better than a home run!

Peavy has always possessed strong control and posted well above average strikeout rates throughout his career. Based on the park factors alone, he may experience a dip in both rates. But overall, the park switch figures to be a positive for his ratios.

Now moving along to the change in teammates, we’ll start with offensive support. The White Sox have been pretty abysmal all year at the plate, having posted a .297 wOBA, which ranks 13th in the American League. They don’t walk or hit for power, which pretty much destroys any potential to score runs. The Red Sox, on the other hand, rank second in the American League with a .340 wOBA, right behind the league-leading Tigers and their .341 mark. There aren’t many team pairs in which the destination team represents as large an offensive support upgrade as Peavy will enjoy. This should do wonders to his win total, though he has actually received pretty decent support in Chicago. He has gotten 4.54 runs of support in his starts, compared to the team’s runs per game average of just 3.70. So his current win rate won’t necessarily get a boost, but his future win potential does.

Last on the checklist is the defensive support. Earlier, I mentioned that all else being equal, he would see a jump in BABIP based solely on the ballpark switch. The White Sox rank 11th in the AL with a -2.1 UZR/150, while the Red Sox are marginally better, ranking seventh with a UZR/150 of exactly 0.0. For what it’s worth, the White Sox team BABIP allowed is actually .291, below the Red Sox mark of .298. Peavy himself owns a .278 mark, so that factors in there, and of course the makeup of each teams’ pitching staff plays a role, so the UZR/150 is probably the more telling metric. This all means that he should see slightly better defense behind him.

So to sum it all up, Peavy moves to a slightly better park, or at least one that is a bit less hitter friendly. He will also benefit from better offensive and defensive support. Looks like a win, win, win. And of course, this doesn’t even include the fact that Peavy’s SIERA sits at a sterling 3.47, well below his actual 4.28 ERA. He should be a pretty good fantasy starter over the final two months.