Diamondbacks manager Torey Lovullo said Wednesday that Walker (elbow) was diagnosed with a torn UCL and will likely undergo Tommy John surgery.
Walker exited his previous start April 14 with forearm tightness and was subsequently placed on the 10-day disabled list. He was later diagnosed with a UCL injury, and a second opinion ultimately confirmed the right-hander is dealing with a tear that will require surgical intervention. This is a brutal blow for both Walker and the Diamondbacks, as the 25-year-old owned a solid 3.45 ERA through three starts for the first-place club prior to suffering the season-ending injury. For now, Matt Koch is slated to start in Walker's place Friday, but Shelby Miller (elbow), who is recovering from a Tommy John procedure of his own, could end up settling in as the long-term rotation replacement by late June or early July.