Mastroianni was originally reassigned to Minor League camp in Spring Training on March 16, and he fared well in four games with Rochester to open the season. He was hitting .450 (9-for-20) with two doubles and two RBIs before getting called up when Oswaldo Arcia went on the 15-day disabled list on Wednesday with a strained right wrist.
"We hope it can continue," Twins manager Ron Gardenhire said. "When he went down [on March 16], he was still having troubles with his ankle and throwing the ball in the outfield. He wasn't quite there yet. But we sent him to Minor League camp, and he got a lot of at-bats and then started off pretty decent."
Mastroianni, 28, played in 30 games with the Twins last year, hitting .185 with five RBIs and two stolen bases. He was limited by a left ankle injury throughout last season, as he originally injured it in Spring Training on a foul tip before having surgery to repair a bone chip in his ankle in May. He then underwent a second surgery on Oct. 17 to remove the fixation hardware initially placed in his ankle.
But Gardenhire said Mastroianni is healthy now, and he's hopeful he can utilize his speed in the outfield and on the bases.
"He told me he feels great," Gardenhire said. "I talked to [Rochester manager] Gene Glynn this morning, and he said he's moving around really good and not favoring his ankle or anything. So that's where we wanted to get him to. We didn't think it'd be this quick, but we need help and he's a guy we like."