Saturday's game in San Diego sees the Diamondbacks needing a fifth starter for the first time in 2010. That change will also mean someone - most likely one of the eight relievers currently on the team - will need to be removed from the 25-man roster.
After the jump, we'll take a look at the possible options in both areas, and assess their strengths and weaknesses.
However, let's start with some realistic hopes for what you will see from a #5 starter. I looked at expected numbers after the 2009 season, and a pitcher at the back of the rotation will generally have an ERA of 5.15 or worse. To put that into the context of a single game, three earned runs over five innings is an ERA of 5.40, and so is around the kind of performance you should anticipate from a #5. Any better than that, such as a quality start, and it's a clear win in terms of pitching.
Moving on to the specific candidates, due to the small sample size available for the regular season to date, the numbers given for each pitcher include both the regular season and spring training appearances. This is a bit of a double-edged sword, but probably gives a better overall picture of how they have performed to date. Here are the three most likely to rise and fall in the coming days - or possibly sooner, with an announcement expected to be made by the Diamondbacks later today.
Coming up from the Aces
9.2 IP, 9 H, 5 R, 3 ER, 5 BB, 7 SO, 2.79 ERA
Benson appears first choice for the spot, not least because he started on Monday, meaning he'd be on his natural rest for Saturday's outing. He allowed a pair of unearned runs, and AJ Hinch said, "It sounds like he executed a pretty decent game plan. There was an error that cost him a couple of runs, but he pitched well." However, Benson is almost completely untried at any level of late: he has only two major-league starts since 2006, allowing eleven earned runs in eleven IP. There are also roster implications. Benson isn't on the 40-man roster, so space would need to be cleared for him there. Additionally, it would be harder to send Kris to the minors, though with Brandon Webb out for the foreseeable future, this is less an issue, at least in the short- to medium-term.
18.2 IP, 21 H, 19 R, 9 ER, 9 BB, 10 SO, 4.34 ERA
As noted by IHSB, Mulvey did start for the Aces on Tuesday, but only worked three innings and 40 pitches, allowing one earned run on two hits and a walk, so would be a viable option for Saturday. He seemed to struggle a bit with his control in spring, walking more batters than he struck out, but in his two starts for Reno, had a K:BB ratio of 5:2. Still a rookie - he won't turn 25 until next month - but with Jon Rauch now the Twins' closer [and with a 1.74 ERA since being dealt there], the trade seems to be favoring Minnesota thus far. IHSB reckons Mulvey will get the call as #5, but I'm writing this piece and so he's my second choice.
23.2 IP, 35 H, 28 R, 28 ER, 9 BB, 21 SO, 10.65 ERA
Buckner's star has fallen fast, since a series of very effective starts in September made him the off-season front-runner for the #5 spot. He had a poor Cactus League, and that carried over into his first start for Reno, on April 11th, when he allowed seven earned runs in five innings. Those came on ten hits, a walk and three wild pitches. Buckner, however, didn't think he threw badly. "They hit some really good pitches and everything else found a hole. I can take away the fact that I threw well today, as stupid as it sounds or as off as it sounds. I'll take my chances 32 starts out of the year throwing the way I threw today." However, I really doubt the Diamondbacks will.
Going down from the D-backs
13.2 IP, 12 H, 9 R, 9 ER, 9 BB, 14 SO, 5.93 ERA
The main reason Vasquez is likely at the head of the table is because he still has a minor-league option, and so can be sent to the minors without having to pass through waivers. He was, notably, the only pitcher not used in the five-hour marathon on Wednesday, likely because he threw 27 pitches the day before. The three-run homer served up there to Andre Ethier certainly dented Vasquez's hopes of enjoying a major-league buffet.
15.1 IP, 22 H, 10 R. 10 ER. 3 BB. 13 SO, 5.87 ERA
Sterling work last night by Rosales, getting the win with two shutout innings in relief, and looked very solid in so doing. That brought back memories of his role in the 18-inning win in Florida, and boosts his chances of staying with the major-league team this weekend. Most of the pre-season projection systems loved him, and I like his K:BB ratio, which now sits at better than 4:1. Overall, he now has a 4.50 ERA in 80 innings, which is an above-average ERA+, so I strongly suspect he wouldn't get through waivers. Keep him.
12 IP, 2 H, 1 R, 1 ER, 11 BB, 10 SO, 0.75 ERA
As in spring training, so in the majors. While Cactus League numbers may have little or no predictive value, the Norberto we've seen so far has basically been the same one seen before Opening Day. While he has a heck of a lot of raw "stuff," there's definitely an issue with regard to Jordan controlling it. My eyebrows were raised at Hinch bringing him in to a tied game in Dodger Stadium, given Norberto had two innings of work above AA, but the inherited runner on second didn't score. If I am still not convinced he is the best left-handed option we have, I suspect he'll get more rope by which to climb up or hang himself.