Mauer believes he will return to the lineup this weekend in Detroit, and Friday's pregame workout will go a long way toward determining when he is back in the lineup.
"Tomorrow, I'm going to get to the park early, give it a real test," Mauer said.
Mauer, who left Sunday's game vs. the Orioles with back spasms, resumed baseball activity Wednesday. Due to mounting injuries to several players, Twins manager Ron Gardenhire worried that the team might be forced to put Mauer on the disabled list to get another healthy body on the roster.
Thursday afternoon, Minnesota optioned Pedro Florimon and Chris Herrmann to Triple-A Rochester. The team will announce corresponding roster moves Friday, one of which is almost certain to be the return of center fielder Aaron Hicks from the seven-day DL.
The roster moves make the possibility of Mauer being placed on the disabled list more remote.
"He's better," Gardenhire said. "We're still looking at the end of this weekend. He believes he'll be able to play by Friday or Saturday, but I think Saturday might be more realistic."
Wednesday's workload didn't overwhelm Mauer, and Gardenhire said his first baseman underwent a similar routine Thursday.
"It went fine," Gardenhire said. "After the game, he was sore from everything he had done, the light swings. But it wasn't like his back's still blown out, just normal soreness from all the rehab stuff he's done. He's going through it again, going to try to do the same stuff."
Stephen Elsesser is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.