The D-backs were hit with a significant blow on Wednesday, as manager Torey Lovullo revealed to reporters that right-hander Taijuan Walker has a partial tear of the ulnar collateral ligament in his right elbow and will require Tommy John surgery (Twitter link via Nick Piecoro of the Arizona Republic). Walker will be out for the remainder of the 2018 season.
Clearly, it’s a huge loss for a D-backs team that watched Walker, long heralded as one of MLB’s most promising pitching prospects, break out with a 3.49 ERA, 8.4 K/9, 3.5 BB/9, 0.97 HR/9 and a 48.9 percent ground-ball rate in 157 1/3 innings last season. The 25-year-old Walker has averaged 27 starts per season over the past three years between the Mariners and D-backs, but Arizona was counting on him taking an even more pivotal role in 2018, joining Zack Greinke, Robbie Ray, Patrick Corbin and Zack Godley in what looked to be one of the National League’s more formidable starting quintets.
[Related: Arizona Diamondbacks depth chart]
Matt Koch will start in Walker’s place on Friday, tweets Zach Buchanan of The Athletic, but he tossed just 56 innings last season and doesn’t have any sort of big league track record. Arizona thinned out its rotation depth in the March trade that saw left-hander Anthony Banda — a largely MLB-ready rotation piece — head to the Rays in the three-team Steven Souza / Brandon Drury swap. Former first-rounder Braden Shipley is still on hand in Triple-A as a potential option, as is recent waiver claim Troy Scribner.
Walker’s injury will now put the recovery of right-hander Shelby Miller under even more of a microscope. The embattled righty struggled through a catastrophic first season in the Diamondbacks organization but looked to be in the process of righting the ship in 2017 before he, too, suffered a UCL tear that necessitated Tommy John surgery. The 27-year-old Miller has yet to pitch in the minors as he continues rehabbing from his own operation, performed early last May, but he could emerge as a viable fifth starter for a talented D-backs rotation at some point in June or July.
The D-backs still control Walker through the 2020 season, and given his reasonable $4.825MM salary as a second-time arbitration player (with Super Two status), the ligament replacement procedure is unlikely to spell the end of his time with the D-backs. Walker’s limited workload in 2018 — he made just three starts and totaled 13 innings — should limit him to a minimal raise in arbitration this offseason. The D-backs will be able to hang onto him for something in the vicinity of $5MM, and while Walker almost certainly won’t be ready to take the hill until at least next May, if not early summer, that’s an eminently reasonable price to pay — especially when considering that he could still be controlled for one year beyond the ’19 campaign.