After spending the offseason looking for upwards of $10M for one year, Roy Oswalt signed for $5M with $1M of incentives. It sounds like he won't be ready to begin throwing in minor league games for 2-4 weeks, so the All-Star break looks to be a reasonable target for his debut. Neftali Feliz is hurt, and struggling, now, so Scott Feldman will fill in until Oswalt is ready, with both Feliz and Feldman likely heading back to the bullpen at that time. How well does Oswalt need to perform to be worth it?
With the $/WAR rate around $4.5M/win, the Rangers are paying for 1-1.5 WAR. If he stays healthy, Oswalt would make 13-14 starts, spanning 75-85 IP. If he can maintain a 4.00 ERA, Oswalt would provide just over a win. Last year in Philadelphia, Oswalt amassed a 3.69 ERA and 3.44 FIP in 139 IP, good for 2-2.5 WAR. He will get around half the innings, which would provide the expected value. Can he repeat his performance of last year?
With an extra-long break after last season, Oswalt may take a while to get back to full strength. He is especially vulnerable to rushing back, knowing he's here to help the Rangers, not the minor league clubs. He also only threw 139 innings due to back problems, his problem area at age 34. His is of the degenerative variety, so it can be treated but it won't ever go away completely.
Statistically, Oswalt posted the lowest K rate of his career last year, only striking out 15.7% of hitters. This was concurrent with a higher contact rate and lower whiff rate. His velocity was down just over a full MPH, which is possible, but unlikely, to come back up now. Moving to the AL will also hinder his ability to increase strikeouts. His best skill is limiting free passes, walking around 6% of hitters in his career, and that rates has stayed fairly constant the past few years.
While Oswalt's walk and strikeout rates shouldn't change much, his HR rate will likely regress quite a bit. Last year, he allowed 0.65 HR/9, a very good rate. He allowed 35.6% flyballs, in line with the previous two seasons, but a HR/FB% of 6.3%, 3% below league average. His career HR/FB rate is 8.8%, so let's set his baseline there. After spending his entire career in the NL, Oswalt shifts to the tougher AL, raising his HR rate to around 9.5%. Houston's ever-changing-name ballpark is HR neutral, and now he's heading to a HR-friendly Ballpark in Arlington, raising that rate to at least 10%. If his HR/FB% would have been 10% last year, he would have allowed four more HR, raising his FIP around 0.40 runs.
Overall, Oswalt will probably have to get a little lucky to be worth the contract straight-up. However, the Rangers can afford to pay more for a win since they are a playoff-level team. The added revenue from being successful, higher attendance and playoff shares, gives the Rangers more able to overpay a bit to get the talent they want. Andy Pettitte did a similar thing this year and has posted very good results so far. If Oswalt is able to stay healthy the rest of the year, the Rangers should be a better team after today.