Projecting Jake Peavy

For major league hurlers, calling Petco Park home is the pitching equivalent of winning an all-expenses paid trip to Disney Land. Bring us your homer-prone, your waiver-wire wanderers, your injury-plagued looking for a fresh start. Petco wishes to help you (sorry, Mark Prior: even the Happiest Pitching Place On Earth has its limitations).

Until July of 2009, right-hander Jake Peavy enjoyed the ambiance of Petco. Make no mistake: Peavy has been a very good starter in his own right. But, his home ballpark surely aided him.

Courtesy of ESPN’s park factor numbers, here’s how much Petco has depressed offense over the past three seasons:

Petco Park, 2007-2009:

Runs: 0.76
HR: 0.72
H: 0.85
2B: 0.73
3B: 0.92

(1.00 is neutral. Numbers under 1.00 indicate a park factor favoring pitchers, and numbers over 1.00 favor batters.)

Petco’s a massive pitcher’s park: that’s not breaking news. But the numbers still are staggering. Run-scoring is absolutely smothered in San Diego’s home ballpark.

Peavy was shipped to the White Sox in a deadline day shocker last July 31st. Here are the three-year park factors for his new home:

U.S. Cellular Field, 2007-2009:

Runs: 1.09
HR: 1.26
H: 0.99
2B: 0.89
3B: 0.61

There aren’t that many doubles and triples legged out in the Cell. That’s because those batters are too busy leisurely trotting around the bases, while Hawk Harrelson shrilly does his best to shatter every window in the greater Chicago area.

Over the past three seasons, Peavy has surrendered 0.44 home runs per nine innings at home, and 1.01 HR/9 on the road. The 28 year-old isn’t an extreme fly ball pitcher (41.8 GB%), but his groundball rate is a few ticks below the league average. Some of those flys that were innocuous outs at Petco are likely to carry over the fence at The Cell.

Let’s assume for a moment that Peavy’s strikeout and walk rates mirror his Bill James projection for 2010: 9.08 K/9 and 2.89 BB/9. But instead of his HR/9 average coming in well under 1.00, he gives up roughly one homer per nine frames. That’s about 24 dingers in his projected 215 innings.

That would make Peavy’s projected Fielding Independent ERA about 3.70.

Maybe you feel that James’ K/9 and BB/9 estimates aren’t quite right. Peavy did cruise once he returned to the mound with the Pale Hose. But those projected K and walk ratios are a dead ringer for his career averages in the N.L., in a pitcher’s haven.

There has been a disparity in the level of play between the A.L. and the N.L. Last offseason, Derek Carty of The Hardball Times examined pitchers switching leagues over the 2004-2008 seasons.

He found that those going from the N.L. to the A.L. received a “penalty.” As one might expect based on the A.L. possessing the DH and clearly playing a superior brand of baseball as of late, pitchers moving from the N.L. to the A.L. saw an across-the-board dip in performance. Pitchers going from the Senior Circuit to the Junior Circuit saw their K/9 decline by 0.57, and their BB/9 increase ever so slightly (+0.05).

Let’s apply those marks to Peavy’s projections. Now, his FIP is about 3.85.

None of this is to suggest that owners should shy away from Peavy. However, it is important to consider park and league effects when projecting a guy moving from a pitcher’s paradise in the N.L. to a homer-happy venue in the A.L. Also, his last two seasons have been curtailed by injury.

Peavy’s good. But if you’re looking for another ERA in the low-three’s, you’ll probably be disappointed.