Fuld's outfield versatility caught the eye of Twins officials.
"He can play all the outfield positions, and he can steal a base," assistant general manager Rob Antony said. "He puts together pretty good at-bats. We got a firsthand look at him when Oakland was in town last week. He's a gamer, a guy who comes to play every day. Hopefully, he can add a little life to the offense."
Fuld was in the Bay Area on Sunday and will join the Twins as they open a series against Tampa Bay on Tuesday night.
The Twins will have a week to possibly work out a deal for Mastroianni. If Mastroianni should eventually be put on waivers and clear, the Twins would be receptive to keeping him in the organization.
"He's in good standing in this organization," Antony said. "He works hard and plays hard. His speed is what you like to see in an extra outfielder. Unfortunately, he came up here and hit a few balls hard, but didn't have any luck."
The Fuld acquisition could give the Twins options should center fielder Aaron Hicks continue to struggle at the plate.
"I don't think [Hicks] is inked in as our everyday center fielder for the rest of the season," Antony said. "He needs to improve his game and become more consistent. He has shown flashes of the things we like to see. And then sometimes he'll kind of get in a fog, slip back into some old habits and doesn't appear as focused as he should be. But we still have a lot of confidence in him and believe he has a world of talent. It's just a matter of him being able to help us right now as well."
Antony said he has discussed with manager Ron Gardenhire the possibility of a platoon situation in center with the switch-hitting Hicks and Fuld.
"I think Aaron is more comfortable from the right side," Antony said. "Maybe we give him more at-bats where he's a little more comfortable and get him going."
Robert Falkoff is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.