The Sabres called up Adam Dennis from Rochester of the AHL to back up Martin Biron for Friday's home game against Florida.
Sabres coach Lindy Ruff said Miller developed soreness during off-ice exercises, and doesn't know how much time he'll miss.
"We don't expect it to be too long," Ruff said following Friday's morning skate. "It's something that flared up on him."
"That's the point of having Marty here," Ruff said. "These things pop up, and Marty's more than capable of playing great games for us."
Biron has started and won three games this season, including Sunday's 4-3 overtime win against the New York Rangers.
Miller emerged as Buffalo's top goaltender last year, and is 9-1-1 with a 2.64 GAA this season. His nine wins tie him for second in the league with four other goalies.
The second-year starter has struggled of late, and has allowed four goals in each of his last three starts following a 3-0 shutout of the New York Islanders.
He missed 22 games last year around this time after breaking his thumb in practice.
Dennis was Buffalo's sixth-round selection in the 2005 draft, and is 4-1 with a 2.40 GAA for Rochester.