During the second inning of Friday's 9-3 Twins victory, Mauer jammed his heel -- also stubbing the sore toe that has plagued him recently -- while legging out a grounder to second base.
"Now, it's just ice and rest," Mauer said. "You'll drive yourself nuts in [the training room]."
Twins manager Ron Gardenhire said Mauer was "day-to-day."
Although he would be eligible to pinch-hit on Saturday, Mauer said he hoped to miss no more than a couple of days. Still, heel bruises can be slow to heal.
"It's pretty sore," Mauer said. "If I was good to go, I'd be in the lineup. It's the impact that hurts."
Drew Butera, the only other catcher on the Twins' active roster, started on Saturday.
"We might be able to go to [Mauer] if I wanted to pinch-hit," Gardenhire said. "But he caught five or six innings after it happened last night.
"Heel bruises can really linger, and we're worried about getting through tonight with only one catcher."
Mauer, the reigning American League MVP and Major League batting champion, played the entirety of Friday's game after missing Thursday's loss to the Tigers.
Mauer is batting .345 this season.
Stephen Ellsesser is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.