Sanchez will get an MRI on Friday, but Ryan is hopeful that it is just a knee strain.
Sanchez appeared to be hurt when he dived head first to end an 8-yard run on New York's second possession of the second half on Thursday night.
He stayed in the game for two more plays before being replaced by Kellen Clemens.
Sanchez was examined by trainers for several minutes on the sideline before he made his way with a slight limp to the locker room. Sanchez was nursing a sore left knee this week after he was hurt in a 17-6 win over Carolina last weekend.
He was 7 of 15 for 104 yards and a touchdown pass against Buffalo.
The Associated Press contributed to this report