FOXBOROUGH, MASS. -- Brett Favre is on the field at Gillette Stadium and doing some work to test out his injured left foot.

Favre appears to be moving a bit gingerly on his fractured left ankle and heel but it's going to be hard to tell much until he's actually facing the Patriots defense. Tarvaris Jackson also is getting some work in after taking the first-team snaps on Wednesday and Thursday.

Jackson also got the snaps in the mock game on Saturday.

Vikings owner Zygi Wilf greeted Favre as soon as Favre took the field. Randy Moss also is warming up as he makes his return to New England.

Meanwhile, CBS studio analyst and longtime NFL coach Bill Cowher said that coach Brad Childress' "credibility is at stake right now. There's no question." Cowher said he belives Favre will be on a short leash today.