Gabbert is under evaluation for a concussion Sunday at Jacksonville, John Glennon of The Athletic reports.
Gabbert took a sack and fumbled -- which the Titans recovered -- midway through the first quarter and left the contest, allowing Marcus Mariota (elbow) to make his first appearance since Week 1. As the only two quarterbacks on the 53-man roster, Mariota will be required to remain in the game unless Gabbert passes his concussion evaluation.