NASHVILLE, Tenn. — Matt Cassel has been a starting quarterback in the NFL. He's also lived the life of a back-up, ready to answer the call when needed.

This is one of those times for Cassel, and the Titans.

Marcus Mariota suffered a fractured fibula in Saturday's loss to the Jaguars, and is out for the season.

Cassel stepped in to replace Mariota against the Jaguars, and he'll be the starter on Sunday in the season finale for the Titans against the Texans at Nissan Stadium.

"I am excited,'' Cassel said. "I am excited to be on the field, I am excited to play with these guys. I am not excited with how the circumstance happened. But at the same time it is part of my job description to be ready and I'll be ready to go next week and we'll go out there and try and win ourselves a ball game."

Cassel completed 13-of-24 passes for 124 yards and a touchdown in relief of Mariota against the Jaguars. He did throw an interception that was returned for a touchdown by Jaguars cornerback Jalen Ramsey late in the game.

On the season, Cassel has completed 14-of-25 passes for 134 yards.

"I think when you get in there the first few series your adrenaline is going a little bit and it starts to calm down and then it is about going out and executing,'' Cassel said. "You don't get the reps during the week and a lot of these weeks went by and you don't get the reps, but to get back out there and play, it felt good.

"Obviously I wish I had one of those throws back. I thought the guy made a great play on the ball. But a part of my job description is to be ready at any point."

Cassel, a 12-year NFL veteran, signed with the Titans earlier this offseason.

He's played with the Patriots, Chiefs, Vikings, Bills and Cowboys in his career.

Teammates expressed confidence in Cassel, who said he'll be ready. Cassel has played in 102 games during his career, with 79 starts. He's thrown for 102 touchdowns and 78 interceptions.

"I have great confidence in him,'' running back DeMarco Murray. "Cassel is a guy who has been around a long time."

A year ago, Mariota's season was cut short because of a pair of knee injuries. He played in 12 games a year ago. Zach Mettenberger started the season finale last season for the Titans, but he was replaced by Alex Tanney in the second half.

"Matt has been doing this for 45 years, so he knows exactly what he is doing. I don't worry about him. I don't worry about (the quarterbacks),'' Titans tackle Taylor Lewan said. "Last game of the year last year (Alex) Tanney came in and crushed it, and I expect Cassel to do the same."