Diamondbacks starting pitching: Seven into five won't go

The Diamondbacks have used seven starting pitchers so far this season, but the ones who've performed best are not the ones you would probably have expected. Indeed, the four best are the ones with least major-league experience, and also being paid close to major-league minimum: the three worst are averaging more than ten times that between them. As we ended the first half, it wasn't an issue, because Brandon McCarthy and Trevor Cahill were both on the disabled list. But they're on the way back: and when they do, it's going to give GM Kevin Towers and manager Kirk Gibson some difficult choices.

Trevor Cahill

Cahill went on the disabled list, July 1st, with what was supposedly a "bruised right hip," caused by a comebacker in a June 19 experience. But I don't think I've seen such a spurious DL stint since we put Russ Ortiz on the DL in June 2005 after a six-game streak with a 7.15 ERA. Gibson said Cahill had shifted his arm angle because he's been compensating for the hip, but that doesn't explain the three starts prior to the injury, where Cahill allowed 23 hits and 15 earned runs in only 14.2 innings. Cahill was scheduled to throw off a mound at Salt River on Monday, but still seems to be some way from a return - and that's assuming they've found out what's actually wrong.

Patrick Corbin

The most telling stat is that the Diamondbacks are 33-43 in games not started by Corbin: it's no exaggeration to say that, if it wasn't for the 17-2 record when he plays, our season would be close to dead in the water. I don't expect him to be that good in the second half: he has been lucky with balls in play (.246 BABIP) and kept them in the park at an unsustainable rare (one HR per 14.5 innings). But, by "that good", I mean a low-two ERA. Based of his strikeout and walk-rate, something in the low three is still quite credible, and I'd happily settle for that. Having carried the team on his back for the first half, it's time for someone else in the rotation to step forward and take up some of the load.

Randall Delgado

Okay, who predicted that, at the All-Star break, Delgado would be the most valuable player we'd get back from the Braves in the Upton trade? No-one? But that's the case, his 0.5 fWAR surpassing that of Zeke Spruill (0.1) or Martin Prado (-0.2). Randall seems to specialize in the borderline quality-start, where he'll go six innings, allowing exactly three earned runs, and kinda keep you in the game. He has had bad BABIP luck (.368), considering his line-drive rate hasn't been excessive (20.3%, NL average is 20.8%). He seems likely to be the first sent back to Reno, when McCarthy returns, but will also be the first in line for a recall, as needed in the second-half.

Ian Kennedy

Jayson Stark gave Kennedy a "Cy Yuk award" for his first-half performance: while not entirely fair (I'd have said Matt Cain has fallen further, and harder), there's no doubt Kennedy has been the biggest disappointment in the rotation. The home-run and walk rates are basically at career highs (the later up almost 50% over his 20-win season in 2011), and Kennedy's strikeouts are down. I think much the same will be true as for Corbin, except in the opposite direction. He'll be better, but I'm not expecting much less than a 4.50 ERA. With an increasing cost and alternatives arriving, there's a distinct possibility our Opening Day starter may not be around next season in Arizona.

Brandon McCarthy

Suffering his traditional late-May shoulder issues, but he begins a rehab assignment with Reno later this week, and will probably get two or three starts there before returning to the club, likely in late July. His first half was certainly a disappointment, but up until his truncated last outing, there were signs he had turned it around - over the four appearances previous to that, he had a 1.19 ERA, including the only complete-game shutout this year by a D-back. His numbers this year remain bloated by his hellacious .404 BABIP in April: if you take that out, he has a FIP of 3.75, which is better than anyone except Corbin. I'm optimistic, if his health holds up - and that's a significant "if".

Wade Miley

After a horrid May, with a 7.34 ERA, Miley has been significantly better of late. Getting his walks down has been key: there's still room for improvement, back to the 1.71 BB per nine innings he delivered last year, but since June 21, he has been almost there, at 1.88. Because he's never going to be a K-meister, avoiding unnecessary base-runners is crucial for Wade, because there will always be hits and homers. That recent control is a large factor in why he has been able to shave a run off his season number since the end of May, thanks to a 2.77 ERA over his last eight appearances. If he can build on that, he should continue to see the numbers going in the right direction.

Tyler Skaggs

On his day, capable of shutting down any line-up in baseball, but Skaggs' problem seems to be consistency; you might also get four-plus innings of mediocre ball. In both stints with the team, he had a great first outing - six shutout innings against Texas, eight against the Rockies. But the second was much less effective, combining for 14 hits and three walks over 10 innings, with eight earned runs. He'll get some more starts while Cahill and McCarthy continue to heal; those will be studied closely, and could help determine his long-term future with the team. I hope he doesn't make the decision an easy one, when it comes time to replace him with one of the veterans.

Conclusion

Delgado being replaced by McCarthy would appear to be the first move, and is one with which I'm fairly comfortable. However, it's the return of Cahill which will present the problem, especially if Skaggs pitches well out of the gates in the second half. The obvious choice would be to thank Skaggs for his service, and return to the rotation which opened the year. But if the NL West division race remains as competitive as it is at this point, the team really needs the "best" five pitchers, working as many games as possible down the stretch, without fear or favor. Who that might be, and whether the team can pull the trigger on it, will be one of the defining stories in the second-half.