The Arizona Diamondbacks are off to a brilliant start this season. They entered play on Tuesday with an 11-4 record, providing them a 2 1/2-game lead in the National League West.

Alas, Arizona's good vibes were harshed prior to the game, as manager Torey Lovullo announced that right-handed starter Taijuan Walker has a "UCL injury." It's not yet clear whether Walker has suffered a tear.

The UCL -- or ulnar collateral ligament -- is most commonly associated with Tommy John surgery. While there are some alternative healing methods -- some pitchers go the rest and rehab route, which tends to involve platelet-rich plasma injections -- it seems more likely than not that Walker is going to miss significant time.

Consider that a disappointing outcome for both Walker and the D-Backs.

Walker, 25, is four starts away from making 100 in his big-league career. Over the first 96, he's managed a 3.96 ERA (105 ERA+) and a strikeout-to-walk ratio near 3.00. In his three starts this season, he'd allowed 15 hits and five runs in 13 innings.

The Diamondbacks, already without Shelby Miller, will have to dig into their rotation depth. That could mean former first-round pick Braden Shipley gets the call. If Arizona looks elsewhere, they could opt for veteran Kris Medlen, waiver-claim Troy Scribner, or perhaps Matt Koch -- he was acquired in 2015's Addison Reed trade. The D-Backs could, in time, turn to prospects Taylor Clarke or Jon Duplantier.

Whatever the Diamondbacks do, they're certain to miss Walker for however long he's out.