Minnesota Vikings running back Adrian Peterson lies on the field after injuring himself on a play in the first half of an NFL football game against the Baltimore Ravens, Sunday, Dec. 8, 2013, in Baltimore. Minnesota Vikings running back Adrian Peterson is carted off the field after injuring his ankle on a play in the second quarter of an NFL football game against the Baltimore Ravens, Sunday, Dec. 8, 2013, in Baltimore. (AP) - Minnesota Vikings running back Adrian Peterson has shed the walking boot on his sprained right foot, but he's not ready for practice. Coach Leslie Frazier says Peterson probably won't practice until Friday at the earliest. The Vikings host Philadelphia on Sunday, and Peterson's status is in question. Frazier says he's more optimistic about backup Toby Gerhart's condition, but he likely won't practice until Friday because of a hamstring injury. At least the Vikings know who'll be giving the handoffs, even if they're not sure who'll be taking them. Frazier named Matt Cassel the starting quarterback for a second straight week. Christian Ponder will be the backup. Dave Campbell on Twitter: http://www.twitter.com/DaveCampbellAP