Mauer, who has been out with a bruised right quad, was not in the lineup for Friday's series opener against the Reds, but made his first plate appearance since June 17, drawing a five-pitch walk in the sixth inning.
Minnesota didn't take any extra risks, calling on Liam Hendriks to pinch-run for Mauer.
Twins assistant general manager Rob Antony said Mauer caught in the bullpen twice Thursday and continues to improve each day.
"He needed to test [his quad] and see how it is," Antony said. "He came walking in and seemed fine to me. He has improved."
Mauer, who is out with a bruised right quad, is not in the lineup for Friday's series opener against the Reds, but is available to pinch-hit.
While there is no set time frame on Mauer's return, Twins manager Ron Gardenhire said his All-Star catcher will return to the lineup whenever he feels ready.
"It's not up to me," Gardenhire said. "All I do is wait for someone to tell me he's ready to go and ready to play. If [Mauer] comes in tomorrow after doing all these bullpens and says 'I'm ready to go, I want to play,' then I type him in. He has to tell me when he's ready and the trainers have to say we're good."
The four-time All-Star and 2009 American League MVP has not made an appearance since June 17, batting .314 with 69 hits and 33 RBIs.