Manager Torey Lovullo said Boxberger (arm) is scheduled to throw a bullpen session Sunday, Zach Buchanan of The Athletic reports.
Boxberger is getting back into a throwing program after a bout of arm soreness forced him to back off of throwing for a little bit. Barring any setbacks in his upcoming bullpen session, the 29-year-old will likely progress to facing live hitters from there before ultimately making his return to Cactus League action. Once healthy, Boxberger will continue to compete with the likes of Archie Bradley and Yoshihisa Hirano for the D-backs' closer role.