Matt Cassel stepped before a bank of television cameras after practice Wednesday at Saint Thomas Sports Park, not long before a renowned surgeon pushed a scalpel into Marcus Mariota’s right leg in an operating room in Charlotte, N.C.

Mariota, the Titans’ young franchise quarterback, would have been the one standing behind that microphone, as he had each midweek practice this season, but is expected to miss four to five months after surgery to repair his right fibula, which was fractured on a sack by Jaguars defensive tackle Sheldon Day late in the third quarter of a season-crushing 38-17 loss Saturday at EverBank Field. Dr. Robert Anderson performed the procedure, which included implanting a metal plate to stabilize the bone.

Cassel, 34, expressed regret about the situation, as the backup prepares for his first start of the season in perhaps his last game with the Titans. The 12-year NFL veteran, who’s gone from Tom Brady’s understudy to big-money starter with the Chiefs to “another coach, basically, in those meeting rooms,” as coach Mike Mularkey put it, signed a one-year deal in March.

He vowed the Titans (8-7) would be ready to play the Texans (9-6) on Sunday in the regular-season finale at Nissan Stadium, a game that’s meaningless in a sense;, since Houston has clinched the AFC South championship and the fourth seed in the playoffs, while the Titans will pack up and go their separate ways. But at the same time, this game means quite a bit. The Titans have an opportunity to finish the season with a winning record and head into the offseason on a positive note. And Cassel has a chance to prove he still belongs in the league, and on this team.

“I think having a guy like myself has worked out well this season,” Cassel said. “I think we’ve got a great room. I’ve got a great relationship with Marcus. Hopefully in some way I was able to help him this year.”

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Cassel helped lead the Patriots to an 11-5 record in 2008 after Brady suffered a significant knee injury in the first game of the season. And although New England missed the playoffs, it thought enough to keep Cassel with the franchise tag before dealing him to the Chiefs. In 2010, he led Kansas City to 10 victories and a division title and appeared in the Pro Bowl.

He’s since compiled an 11-23 record as a starter with the Chiefs, Vikings, Bills and Cowboys.

The Titans are playing to win Sunday and believe Cassel provides the best opportunity to do so.

Alex Tanney, 29, who played well in the second half of the finale last season in relief of struggling Zach Mettenberger, has been promoted from the practice squad to serve as the backup.

Beyond on-field performance, there is value in having a veteran serve as the primary backup quarterback, particularly when the starter is, like Mariota, in his early 20s.

Cassel’s experience allows Mariota to pick his brain in those meeting rooms, and the veteran has embraced that aspect of the job.

“I was a young guy with Tom and he kind of took me under his wing and was very helpful in my development, very helpful in being a mentor to me,” Cassel said, “and we still talk all the time to this day. When I got older, I always told myself I would like to do the same if I had that opportunity.”

Mariota’s surgery was “completed late this afternoon and from those involved, considered a success,” the Titans announced Wednesday night. He is expected to heal in time to participate in organized team activities and should be OK for the start of training camp in July.

Whether Cassel remains around remains to be seen.

But on this day, same as always, he was in the meeting room bright and early. Before stepping on the practice field, he pulled out his cellphone and began typing a message to Mariota, the man he’s replacing as the Titans’ starting quarterback for the week.

“I sent him a text,” Cassel said, “and told him we missed him and we’re thinking about him, praying for him and hoping that everything goes well for him.”

Then the veteran set his sights on defeating the Texans, and blocked out any questions, internal or external, about his future beyond Sunday.

Injury updates: Titans cornerback Jason McCourty (shoulder/chest) and linebacker Sean Spence (illness) did not practice. Tight end Jace Amaro (quad) was limited. Cornerback LeShaun Sims was a full participant but has yet to clear the league’s concussion protocol.

Defensive lineman Karl Klug was scheduled to have surgery to repair a torn left Achilles on Wednesday.

Roster moves: The Titans placed rookie defensive end Mehdi Abdesmad on injured reserve with a high ankle sprain and promoted nose tackle Antwaun Woods from the practice squad. The team also added outside linebacker Kourtnei Brown and wide receiver K.J. Maye to the practice squad.

Ramsey award: Jaguars cornerback Jalen Ramsey was named AFC Defensive Player of the Week for his performance in last week’s 38-17 victory against his hometown Titans.

The Smyrna native and Brentwood Academy graduate returned an interception for a touchdown and allowed four catches on 10 targets for 20 yards, according to the analytics website Pro Football Focus.

Reach Jason Wolf on Twitter @JasonWolf and on Instagram and Snapchat at TitansBeat.