The linebacker, who led the team with nine tackles, left the game with the injury in the third quarter.
Teammate Antonio Smith told reporters: "I spoke to him and he said he's doing good. [Cushing's exit from the game] kind of threw me off.
"Knowing who Brian is, the thing I would say changed is, he's an animal, he's everywhere on that field and you seen that in the first half that if anybody was coming up the middle, he was laying that hat on them."
The Seahawks went on to win the game 23-20 in overtime.