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The Diamondbacks are moving in a new direction after several years wandering the (figurative) desert. New GM Mike Hazen didn't waste any time shaking things up: He swung a trade for the Mariners' Taijuan Walker, then cut ties with veterans Welington Castillo and Rubby De La Rosa. After a 69-93 finish in a year when some thought the Diamondbacks could break through to the playoffs, a bit of late-autumn cleaning might make sense.
However, in tossing out Castillo's pungent bathwater, Hazen may have also disposed of a perfectly good baby in De La Rosa. (Yes, I know that's a strained metaphor, but given my colleague's egregious meat puns, I think it's more than fair.) While he certainly didn't star in 2016, De La Rosa could have the talent to become a dependable mid-rotation starter.
An obvious issue arises with De La Rosa: health. Back in 2011, he underwent Tommy John surgery to treat an ailing elbow. Over the subsequent years, he managed to stay on the mound, but that changed in 2016 when his elbow flared up again. After missing a few months, he elected to try stem cell therapy in September; his future for now is somewhat uncertain. If his elbow recuperates, though, he might be able to sustain this tantalizing trend:
As it turns our, those strikeouts made him a pretty good pitcher. Prior to 2016, De La Rosa had a career DRA- of 104 and cFIP of 101. This season, though, he improved to an 82 DRA- and 85 cFIP, besting Rick Porcello and Madison Bumgarner (among many others) in both regards. Those results came over just 50.2 innings, and if he could maintain them over, say, 180, he'd be a welcome addition to any big-league rotation.
How did De La Rosa take this step forward? He started throwing his breaking ball a lot more often:
Out of 206 hurlers with at least 200 sliders, de la Rosa's ranked 28th in swinging-strike rate at 22.2 percent; that clip obviously played a large role in his strikeout spike. The slider also had an immaculate 69.0 percent strike rate, which placed him 46th in that sample. Thanks to that combination of strikes and whiffs, De La Rosa's slider was the best on the Diamondbacks — even superior to that of Zack Greinke, his ace teammate.
Earlier in the season, before De La Rosa's injury sidelined him, Diamondbacks catcher Chris Herrmann talked with the Arizona Republic's Nick Piecoro about the slider. He cited improved command as a big factor in the slider's improvement, remarking that De La Rosa was "starting to get a good idea of where his ball is going now." Velocity's never been an issue for De La Rosa's slider, so now that he can control it better, he's able to unleash it whenever he pleases.
Now, De La Rosa might not be able to continue pulling this off. Some evidence suggests heavy slider usage can lead to injuries, which could explain the elbow maladies he's dealt with this year. Those could just be a coincidence, though. He's always had a high-octane fastball, and now that he's learned to pair that with a devastating slider, he's become an above-average major-league starter — a rare, and thus lucrative, occupation.
So why did Arizona part ways with De La Rosa? Perhaps they know something about his elbow the rest of us don't. Or maybe Hazen is following in the footsteps of his short-sighted predecessor. Whatever the reason, the righty's breakout in early 2016 makes him worth a one-year gamble for a team in need of a starter.
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Ryan Romano is the co-managing editor for Beyond the Box Score. He also writes about the Orioles for Camden Depot, and about politics for The Diamondback. Follow him on Twitter if you enjoy angry tweets about Maryland sports.