As feared, Delanie Walker is going to miss a significant chunk of time.

The Titans placed their three-time Pro Bowl tight end on injured reserve Monday after Walker suffering a gruesome ankle injury in the Titans' 27-20 marathon loss to the Dolphins in Miami.

Walker went down awkwardly as safety TJ McDonald tackled him late in the fourth quarter. His right leg snapped back and his ankle buckled before he began to writhe in pain.

Trainers immediately tended to him. Moments later, with a towel draped over his head, Walker was carted off the field with his right leg in an air cast.

Players placed on injured reserve could be eligible to return later in the season.

A sixth-round draft pick in 2006, Walker signed a two-year extension in July worth $17 million that runs through 2020, when Walker will be 36.

Jonnu Smith is now thrust into a critical role. The second-year tight end started 13 games last year and had 18 catches for 157 yards and two touchdowns as a rookie. The Titans also have tight ends Luke Stocker and Anthony Firkser on their 53-man roster.

Titans add tight end MyCole Pruitt

Also on Monday, the Titans signed tight MyCole Pruitt to their active roster. Pruitt had been on the Texans practice squad.

A fifth-round selection by the Vikings in the 2015 NFL draft, Pruitt has 12 catches for 102 yards in 21 games of NFL experience with the Texans, Bears and Vikings.

Reach Erik Bacharach at ebacharach@tennessean.com and on Twitter @ErikBacharach.