The Diamondbacks announced Thursday that right-hander Kris Medlen will start for the club tomorrow against the Astros. Arizona stopped short of formally announcing that Medlen’s contract has been selected, though they’ll need to make that move after today’s game and, with it, also make a corresponding 40-man roster move. That could be accomplished simply by transferring Taijuan Walker from the 10-day DL to the 60-day DL in the wake of Walker’s season-ending Tommy John surgery.

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In addition to Walker’s season-ending injury, Arizona recently lost southpaw Robbie Ray to the disabled list for the foreseeable future due to a strained oblique muscle. With that pair out of the picture for now, the Snakes will rely on Zack Greinke, Patrick Corbin, Zack Godley and Matt Koch to complement the newly promoted Medlen in their rotation.

Once a rising star in the Braves’ rotation, it’s been a half decade since Medlen was an effective big league starter. The 32-year-old Medlen logged a 2.75 ERA in 445 innings with Atlanta from 2010-13, missing the bulk of the 2011 season in middle of that stretch while recovering from Tommy John surgery. He looked to have bounced back with strong 2012-13 performances, but Medlen again sustained a torn UCL prior to the 2014 season and was again forced to the sidelines for more than a year.

The Royals attempted to buy low on the talented righty following that injury, but Medlen managed just a 5.12 ERA in 82 2/3 innings over the life of a two-year deal in Kansas City. He spent the 2017 season back in the Braves organization but didn’t end up appearing at the Major League level.

Medlen has struggled through 18 innings with the D-backs’ top affiliate in 2018, pitching to a 6.00 ERA, albeit with a more encouraging 18-to-8 K/BB ratio in that time. At this point, it’d be a stretch to expect him to ever return to the promising form he showed prior to his second ligament surgery, though it’s certainly plausible that he could yet be a serviceable source of innings at the MLB level. Given that Ray should return from his injury at some point in June, it seems likely that Medlen and Koch will soon be vying for a single spot in Arizona’s mix of starters. Shelby Miller, too, is on the mend from Tommy John surgery, however, and could eventually pair with Ray to push both Koch and Medlen out of the starting picture at the big league level.