"The Vikings downgraded running back Adrian Peterson from doubtful to out Saturday for today's game at Atlanta.

Peterson was unable to regain his usual explosive running and cutting style after suffering a high ankle sprain in the first quarter of last week's 27-21 loss to Oakland. Trainers were not encouraged he could play based on the week's rehab work.

Backup Toby Gerhart will get his first start of the season against the Falcons.

At 2-8, the Vikings want to protect their most valuable asset in Peterson, who signed a seven-year, $100 million extension in the offseason. "