The Vikings' running back had been listed as probable to play with a finger injury. Peterson was limited in practice on Wednesday and Thursday, but was full go on Friday and appeared fine to play.
Peterson was subsequently downgraded to questionable on Saturday.
The Vikings' official Twitter feed showed the team boarding a plane leaving for Detroit hours before announcing Peterson was downgraded, so we presume he made the trip and will receive treatment overnight. We do not yet have word on the severity of the illness.
Peterson has averaged 107.1 rushing yards per game in his career against the Lions. In their first meeting in Week 2, Peterson compiled 134 rushing yards on 29 carries. He totaled 192 scrimmage yards.