"He came in and got to the park early and did some stuff and said he wanted to play," Gardenhire said. "The trainers said the same thing. He feels good and can run all the bases and all those things."
Gardenhire added he was relieved Mauer was able to avoid the 15-day disabled list, as it would've kept him out of action until May 20 against the Padres.
"With backs, it's something you don't want to deal with too much," Gardenhire said. "When you start feeling better, you always want to give it a few extra days. I've had it and we've all had it, and it's just not very fun. So I'm just happy to see him in here, wanting to play."
Mauer didn't know if he'd play until Saturday morning, but he was available to pinch-hit late in Friday's 2-1 win. After Saturday's game, he said he was still feeling some stiffness in his back.
"It was good to get back out there, definitely," Mauer said. "I still feel it, and I'm pretty stiff right now, but it feels pretty good to be back out there. I know it was just a few days, but it felt like forever. It was a lot of time in the training room to try to get back out on the field."
Mauer is scheduled to receive more treatment on his back at the team hotel on Saturday night, and he said he expects to be back in the lineup on Sunday, but isn't sure if he'll be at first base or designated hitter.
"We'll see what happens when I get to the park tomorrow," Mauer said. "But I'll be in the lineup in some capacity, which is good."
Rhett Bollinger is a reporter for MLB.com. Read his blog, Bollinger Beat, and follow him on Twitter @RhettBollinger. This story was not subject to the approval of Major League Baseball or its clubs.