Titans quarterback Marcus Mariota fractured his right fibula on Saturday against the Jaguars, the team announced.
Mariota will have surgery on his fibula on Wednesday and his recovery is expected to take four to five months, according to ESPN's Adam Schefter.
Mariota was carted off the field with an air cast on his right ankle in the third quarter of Saturday's game. Mariota was sacked by Jaguars defensive lineman Sheldon Day before going down with the injury, and the team immediately ruled him out from returning.
The Titans were losing 25–10 when Matt Cassell took over as quarterback. He threw a touchdown in the fourth quarter to make it 25–17, but the Jaguars won the game 38–17.
Mariota, 23, has thrown for 3,426 yards and 26 touchdowns through 15 games this season.
With the loss, Tennessee dropped to 8–7 on the season, with the AFC South–leading Texans (8–6) still to play on Saturday night against the Bengals. The Texans can clinch the division with a win.