This news comes a day after Walker was diagnosed with a UCL injury. Walker had a second opinion on the injury today, which confirmed that he had a tear. The injury will force him to miss the rest of the season.
The 25-year-old Walker was entering his second full season with the D-backs after he was acquired from the Mariners during the Jean Segura deal. Walker, who spent parts of four seasons in Seattle, managed to post a career-best 3.49 ERA and 8.4 strikeouts per nine innings while going 9-9 in 157 1⁄3 innings pitched across 28 starts with Arizona. This year, he has a 3.46 ERA in 13 innings across three starts.
Without Walker, the D-backs rotation is going to hurt even more since they are already without Shelby Miller. Outside of ace Zach Greinke, they only have Robbie Ray, Patrick Corbin and Zack Godley. Matt Koch will take Walker’s place on the staff and will start on Friday when they begin a three-game set with the Padres. Koch has only eight games of big league experience after pitching in seven games in 2016 as a reliever and one last year. In 2017, he split time in Triple-A Reno and Low-A Hillsboro, but did not fair well at either level after posting a combined 7.71 ERA in 56 innings across 12 starts.