EDEN PRAIRIE — The Minnesota Vikings have ruled Christian Ponder out for Sunday’s game at Baltimore, because the quarterback has not yet passed all of his post-concussion tests.

Coach Leslie Frazier said Friday that Ponder will not suit up against the Ravens, with Matt Cassel starting and Josh Freeman backing him up per the plan set at the beginning of the week.

This is Ponder’s third significant injury of the season. He had a broken rib that paved the way for Cassel to start against Pittsburgh on Sept. 29, and dislocated his shoulder at the end of the third quarter against Washington on Nov. 7. Ponder took a hit to the head late in the second quarter last week against Chicago.

Running back Adrian Peterson returned to practice Friday after taking the last two days off to rest his sore groin, following the pattern that has developed in the second half of the season to keep him fresh.

“No real need to burst or go 100 miles per hour today, but just something to make him feel comfortable about Sunday,” Frazier said.

Peterson was listed as questionable on the injury report, but there’s no indication of doubt about the NFL’s leading rusher’s participation in Baltimore. He has 1,208 yards through 12 games.

Safety Harrison Smith is still on injured reserve because of the turf toe injury he suffered nearly two months ago, but he practiced all week and is on track to return to the active roster and play Dec. 15 against Philadelphia.

Also, wide receiver Greg Childs, working his way back from bilateral patellar tendon tears, took part in consecutive practices this week for the first time. Frazier said he’s “really improved.” Childs is on the physically unable to perform list, and the Vikings must decide by Monday whether to place him on the active roster, put him on injured reserve or cut him.