Manager Torey Lovullo said Monday that Gallen is scheduled to start on Tuesday against the Oakland Athletics. The 25-year-old was the Diamondbacks' best pitcher last season and finished ninth in the National League Cy Young voting after finishing the abbreviated 2020 season with a 2.75 ERA and 82 strikeouts over 72 innings.
Gallen was hurt during spring training while taking batting practice, saying he got jammed by an inside pitch.
Lovullo also confirmed on Monday that the D-backs had signed veteran Josh Reddick to a minor league deal and that the veteran would report to the team's alternate site in Scottsdale, Arizona.
The 34-year-old Reddick has 144 career homers over the years with the Astros, A's, Red Sox and Dodgers. Reddick hit .245 last season with four homers and 23 RBIs.