"I had a little setback early in the third quarter," Roethlisberger said Wednesday while speaking with reporters, adding that he's working with trainers and doctors to get the ankle back in shape.
Roethlisberger was limited in practice and walked into the trainer's room afterward with a noticeable limp.
"We got set back about a week," he said.
In a conference call with reporters, the quarterback said that on a scale of 1 to 10, his ankle was at a 5, according to The Denver Post.
Next in line on Pittsburgh's depth chart is Charlie Batch, who started in place of Roethlisberger and threw for 208 yards and one interception in a 27-0 victory over the St. Louis Rams in Week 16.
Along with Roethlisberger, center Maurkice Pouncey (left ankle) also was limited in practice Wednesday. Linebacker James Harrison (toe), defensive end Brett Keisel (right groin), running back Mewelde Moore (sprained left knee) and safety Troy Polamalu (right calf) didn't practice. All but Moore are expected to play against the Broncos.
The Associated Press contributed to this report.