Vikings head coach Leslie Frazier is not ruling out running back Adrian Peterson although he is not expected to practice until Friday at the earliest due to a foot injury that he suffered in last Sunday's loss to Baltimore.

Adding salt to the open wound is that backup running back Toby Gerhart is dealing with a hamstring injury. He, too, is likely sidelined until Friday although Frazier likes Gerhart's chances of being ready for Sunday's game compared to Peterson's.

"I'm more optimistic with Toby than I am with Adrian," Frazier told reporters at a press conference earlier Wednesday.

Don't tell that to Peterson, who ranks second in the league to LeSean McCoy in rushing yards.

"He said, 'I'll be ready to go coach,'" said Frazier, who did note that Peterson is a fast healer.

There is no question, however, regarding who will start at quarterback for the Vikings. Matt Cassel will get the start and Christian Ponder is the backup.

"I feel like he did some good things in that game on Sunday (against Baltimore)," Frazier said. "We're going to give him an opportunity to get back-to-back starts and look forward to him leading us to victory on Sunday."

This will be Cassel's fourth start of the season for Minnesota. Last Sunday, Cassel completed 45 percent of his pass attempts for 265 yards and two touchdowns in a wild and snowy back-and-forth affair that featured the most lead changes in NFL history. Ponder has started nine games. He suffered a concussion two weeks ago against Chicago, but has been cleared to return. Josh Freeman was signed as a free agent earlier this season after being released by Tampa Bay and started in one game.