Titans' Delanie Walker has broken ankle, ligament damage

Tennessee Titans tight end Delanie Walker suffered a broken ankle and ligament damage on Sunday and is not expected to play again in 2018, a source told ESPN's Adam Schefter.

The Titans placed Walker on injured reserve Monday but did not disclose the nature of his injury. The team signed tight end MyCole Pruitt off the Houston Texans' practice squad in a corresponding move.

Titans coach Mike Vrabel said Walker had a "leg injury" and would undergo surgery in the next couple of days.

Meanwhile, Vrabel said Taylor Lewan is under concussion protocol and he was adamant about the left tackle not doing anything until he is cleared. As for the hit by Miami Dolphins defensive lineman Andre Branch, Vrabel said he didn't feel it was dirty but "absolutely" thought Lewan was targeted.

Vrabel also said quarterback Marcus Mariota's elbow injury is still being evaluated and they're hopeful about getting a good report back. He and general manager Jon Robinson have discussed adding another quarterback if needed.

Walker caught a 15-yard pass from backup quarterback Blaine Gabbert and went down awkwardly as he was tackled by Dolphins safety T.J. McDonald in the fourth quarter of a 27-70 loss. Trainers put a towel over Walker's head as they fitted him with an air cast for his right leg before lifting him onto a cart and taking him to the locker room.

The Titans signed Walker to a two-year, $17 million contract extension ($12.76 million guaranteed) before the season.

Walker, 34, was selected to his third straight Pro Bowl in 2017, when he led the Titans with 74 receptions and 807 receiving yards. He and the Kansas City Chiefs' Travis Kelce are the only tight ends with at least 800 receiving yards in each of the past four seasons.

The 2018 season is Walker's 13th in the NFL and sixth in Tennessee. Over the previous five seasons, he had 356 receptions -- the most by a tight end.

ESPN's Turron Davenport contributed to this report.