The Titans' season may have just ended. Quarterback Marcus Mariota's season is definitely over, the team announced after Saturday's 38-17 loss to the Jacksonville Jaguars.

Late in the third quarter, with Tennessee trailing Jacksonville 25-10, Mariota was sacked from behind by Sheldon Day. It looked innocuous enough at the time, but the Titans' medical staff had to apply an air cast to Mariota's leg and he left the field on a cart.

The Titans initially called it an ankle injury. However, after the game Mike Mularkey told reporters that Mariota had suffered a fractured fibula.

Stepping in for Mariota: veteran journyeman Matt Cassel, who had appeared in just two games this season and thrown just one pass. Cassel had some success upon entering the game, going 13 for 24 for 124 yards with one touchdown and one interception. Mariota completed just 8 of 20 passes for 99 yards and a touchdown. Neither performance was good enough.

It'll be Cassel under center for the Titans in Week 17 against the Texans, who can lock up the AFC South with a victory against the Bengals on Saturday night. If Houston can't get the win at home, their Week 17 matchup with Cassel the Titans will be for the division title and the playoff spot that comes with it.