Blaine Gabbert had to leave the Jacksonville Jaguars' practice early after sustaining an ankle sprain.
The quarterback, who is competing with Chad Henne to be the team's starter, picked up the injury towards the end of Monday's session.
Head coach Gus Bradley told reporters: "A freak deal. He got up and he walked off, and that's a good thing."
Gabbert is due to undergo further tests to determine when he will be able to return to training camp.