Diamondbacks manager Torey Lovullo confirmed that Walston will be called up from Triple-A Reno to start Sunday's game against the Marlins, Alex Weiner of ArizonaSports.com reports.

EDGE Analysis

He'll step into the rotation spot vacated by Slade Cecconi, who was optioned to Reno earlier in the week. Walston will be making his first MLB start and second MLB appearance Sunday after he was charged with two earned runs on three hits and four walks while striking out five over 3.2 innings in a long-relief appearance May 1 against the Dodgers. The 22-year-old lefty has been a member of the rotation for Reno for much of the season, logging a 4.54 ERA, 1.68 WHIP and 35:20 K:BB across 35.2 innings in the hitter-friendly Pacific Coast League.