The Minnesota Vikings have some concern about quarterback Sam Bradford's left knee but remain cautiously optimistic about his status for Sunday's game, a source told ESPN on Friday. Bradford on Tuesday had an MRI on the knee after another source told ESPN that the quarterback had experienced swelling, some pain and discomfort in the left knee after Monday night's victory over the New Orleans Saints. According to the source, the MRI did not reveal any specific damage, but said scans do not always offer a clear picture in a knee that has undergone multiple ACL repairs. It is the same knee that underwent ACL repairs in 2013 and 2014 when Bradford was with the Rams. Bradford has been listed as a limited participant on the team's practice reports all week, but the source said the thought was that Bradford would be able to play when the Vikings visit the Pittsburgh Steelers on Sunday. Case Keenum is the backup and has gotten an increased workload in...