X-rays on Hernandez's ankle were negative, and the Patriots believe the injury to be a high ankle sprain, a source who was briefed on the tight end's injury told NFL.com and NFL Network's Albert Breer.
After the game, Hernandez was seen in the locker room with crutches and a walking boot on his right foot, according to the Boston Herald.
Hernandez remained down on the field for several minutes before being helped down the stairs into the Patriots' locker room with a trainer on each side of him.
The injury to Hernandez led to the Patriots switching to a three-receiver grouping against the Cardinals. This opened the door for Wes Welker, who didn't get on the field for the first four minutes of the game.
Follow Dan Hanzus on Twitter @danhanzus.