New England receiver Wes Welker went down clutching his left knee after catching a pass and taking it for a 12-yard gain early in the Patriots' first drive of the game against the Texans. He appeared to be in a great deal of pain, was helped off the field by Patriots trainers and was taken to the bench. He later was brought on a cart to the locker room. Source: SportingNews.com
there was no contact, his leg just planted in the grbutt. The Patriots are still playing for something so no one can be blamed.
Similar to Kevin Smith's season-ending ACL injury. He wasn't touched. Just hurt his leg trying to make a move.