Peterson suffered the injury during the Vikings' Week 11 loss to the Oakland Raiders and has not practiced in the two weeks since the injury. Frazier told reporters Peterson has improved, although cutting on the ankle is still an issue.
"He's much further along than he was a week ago, so hopefully in the next few days, being able to cut will be less of a problem than it is today," Frazier said.
While Peterson's status is not much of a surprise, wideout Percy Harvin was unexpectedly absence from practice Friday. Frazier said Harvin's illness is not migraine-related, but would not disclose the exact issue. Harvin has been plagued by migraines during his three NFL seasons.
"I know they're evaluating Percy and determining what's going on," Frazier said. "They told me we're evaluating the situation and we'll let you know when we get back in. But everything that's been indicated to me is he's fine and nothing like what we've experienced in the past."
Harvin officially was listed as questionable with an illness after practicing the previous two days.
"Please, please, please, let's not go down that road," Frazier said at the suggestion Harvin wouldn't play. "We need No. 12 out there. We need him."
Broncos running back Willis McGahee returned to take part in full practice Friday after sitting out Thursday with an illness and is probable. Linebacker Von Miller (thumb) and wide receiver Eddie Royal (toe) took part in a limited portion of practice and are questionable.
For a complete look at all injuries around the league, go to NFL.com's injury page.