Yesterday, the Angels acquired 29-year old southpaw Jason Vargas from the Seattle Mariners. Vargas has performed at just about a league average level according to ERA- in half of his four seasons with the M’s. Let’s see how the ballpark switch might affect his results.
Before delving into the relevant park factors, it is worth noting that Vargas has outperformed his SIERA for three straight seasons, and done so handily in two of those. He was fortunate in each luck metric (BABIP, LOB%, HR/FB) at least once during those seasons and has not posted a BABIP above .285 in all four of his years in Seattle. Ignoring the ballpark for the moment, some of that low BABIP could be attributed to the strong Mariners outfield defense over the years combined with Vargas’ fly ball tendencies. The good news is that he’s going to continue having strong outfield defense behind him, just the players and uniforms actually playing will change.
Now let’s get to the park factors (2012 factors from Statcorner.com):
|RHB K||LHB K||RHB BB||LHB BB||RHB 1B||LHB 1B||RHB HR||LHB HR||RHB Runs||LHB Runs|
Who knew that SAFECO actually increased strikeouts? Sure enough, Vargas’ strikeout rate at home was well above his away mark in each of his Seattle years, except for 2010, when it was similar. That means that Vargas could see a dip in strikeout rate due to park factors. Since his strikeout rate is already low to begin with, any further drop could make it difficult for him to generate positive fantasy value.
Aside from inflating strikeouts, SAFECO also boosts walks. Unlike the difference in strikeout park factors, this is actually beneficial to Vargas. Similar though to how he performed home and away in strikeouts, his walk rate was better in away parks in three of his four Seattle seasons. Though his F-Strike% this season did not match up with a walk rate as low as he posted, the park switch should help offset any regression he might have seen.
The singles park factors are relatively similar for both parks, but home runs is where we see another difference. While SAFECO field crushes right-handed home run power, it’s not so terrible against lefties. Angel Stadium, on the other hand, plays similarly to hitters no matter which side of the plate they hit from. If you weighted the handedness factors to come up with an overall home run park factor, Seattle likely reduces long balls a bit more, but both clearly are bad for power. As such, Vargas should not experience a significant difference in HR/FB ratio simply as a result of park factors. In addition, since his HR/FB ratio was a high 12.8% this season, he would likely see that decline no matter where he pitches in 2013.
The last park factor is overall runs scored and that obviously takes into account other events such as doubles and triples. We see here what we pretty much already knew — SAFECO Field is a pitcher’s haven. I’m not sure exactly what Angel Stadium’s reputation is, but it’s pretty clear that it’s quite favorable to pitcher’s as well, just not at the extreme level SAFECO is.
So taking everything together, park factors should reduce Vargas’ strikeout and walk rates while increasing his ERA. However, given that the Angels have a significantly better offense, his win total should rise. Whether the additional value earned from those extra wins is enough to offset the loss of strikeouts and higher ERA, I don’t know. But he still remains someone I have no desire to draft for my fantasy team.