Newly acquired Blue Jays pitcher Jesse Chavez has had a nice little run with the Athletics over the past two years. In 303 innings mostly as a starter, he's posted a 3.83 ERA (100 ERA-), backed up by a 3.87 FIP (100 FIP-), 3.78 xFIP (96 xFIP-) and 3.82 SIERA. Taken together, this suggests Chavez is basically a league average starting pitcher (if not an innings eater), and there's been nothing particularly fluky about his results, even on a park adjusted basis.
That park adjustment is important, since Oakland's O.co Coliseum is one of the best pitcher parks in baseball. Over the last five seasons, Oakland pitching has allowed a 3.29 ERA at home, with a .288 wOBA allowed. On the road, those same pitchers have allowed a 3.99 ERA and .314 wOBA allowed. Even more significantly, that difference is due almost entirely to differences in managing contact: there's no difference in strikeout rate, and just a small 0.5% increase in walks on the road.
This has obvious implications for the Jays' acquisition of Chavez, since to paraphrase, Dorothy's not in Kansas anymore. So let's look at his splits:
Chavez's differential of 36 points between his home .293 wOBA and his road .329 wOBA is greater than the average for Oakland pitchers of 26 points. That's despite the fact that his strikeout rate and walk rate (as usual, BB+HBP-IBB) are actually better on the road. That net home/road differential breaks down into roughly -18 due to K and BB, and +54 due to contact. That contact differential is roughly double the average Oakland pitcher recently.
And we can see why: it's basically all about power. The next set of column show each outcome as a percentage of all balls put in play. His rate of singles is a little higher on the road, but only 1% higher. His doubles and triples are 1.7% higher, but off a much smaller base, so while it's only a 1.7% percentage point difference, it means he allows 40% more doubles. The same of true of home runs: a 1.7% increase off an even smaller base is 60% more home runs. This is...not good.
But it gets worse. The AL West is home to a bunch of pitchers' parks, such that the road stats of a player in that division are disproportionately accumulated in pitcher's parks. For example, of Chavez's 33 road games, six - almost 20% - have been in Angel Stadium, another great pitcher park. So let's further split the road games into the pitcher parks he's played in (Atlanta, Kansas City, both Los Angeles, Miami, Seattle, San Francisco, Tampa Bay), and all others:
That breaks the road sample almost in half (which means almost 75% overall in pitcher parks), though with caveat we're getting into pretty small sample sizes. Even in the road data, there's a significant difference in wOBA of 23 points. To put that .337 non-pitcher park road wOBA in perspective, Russell Martin had a .340 wOBA last year.
At a more granular level, the data gets pretty weird, starting with strikeouts and walks. As in Oakland, in road pitcher parks Chavez is almost perfectly league average in both. In hitter parks, he's been elite, with an almost 4:1 ratio. He's given up a lot more damage on balls in play, but it's not really on a power side. He's given more up home runs, but at the expense of doubles--that hurts a little, but it's not a big deal. Instead, he's given up way more singles, both relative to elsewhere and league average.
This is all very weird: could it be a fundamental difference in approach? Again, very small samples, but in non-pitcher road parks, Chavez has a 47% ground ball rate against just 33% fly balls. In pitcher road parks, it's 39% to 40% (in Oakland, 43% to 33%, which is roughly his overall rate and the league average). My guess is it's mostly noise: getting strikeouts and ground balls and preventing free passes are a good thing everywhere, so why would he not do it all the time if he could? But if you want to make a bull case for Chavez, this is really it. His profile been completely different in neutral or hitter parks on the road the last two years.
My guess is a lot of regression is due, and he's neither going to be an elite K/BB pitcher on the road, nor be a ground ball machine, nor get singled (BABIP'd) to death. Net-net, that leaves him as a backend rotation type with durability issues who is susceptible to power, pitching mostly in parks which are conducive to doing that. His profile is very much tailored to pitching in Oakland and the AL West, and it's the exact type of profile I wouldn't bet on in the AL East.