After the injury on Sunday, Walker had been carted off after his ankle "looked to bend at an awkward angle," per reporter Paul Kuharsky.
Rapoport added more context:
During the 2017 regular season, the veteran registered 74 receptions for 807 yards and three touchdowns.
Walker was named to the Pro Bowl at the conclusion of both the 2015 and 2016 seasons with his best career campaign coming in 2015.
He set career highs with 94 receptions for 1,088 yards and hauled in six touchdowns as well.
Walker followed that up in 2016 with 65 grabs for 800 yards and a personal-best seven touchdown receptions.
It didn't take long for Walker to become quarterback Marcus Mariota's favorite and most-trusted target in the passing game, and that has continued to be the case.
Walker was originally a sixth-round pick in the 2006 NFL draft by the Niners out of Central Missouri State, and he was little more than a complementary part of the offense for most of his tenure behind starting tight end Vernon Davis.
He showed flashes of brilliance and explosiveness in limited opportunities, however, prompting the Titans to sign him and make him their full-time starter entering the 2013 season.
That has proved to be a fantastic move on Tennessee's part, but it finds itself in a difficult situation in terms of having to replace Walker after this setback.
Although he is nowhere near the same level as Walker, second-year man Jonnu Smith would likely be the biggest beneficiary at tight end with his teammate out.
Wide receivers Rishard Matthews, Corey Davis and Taywan Taylor would also become an even bigger part of the offense.
The Titans have more weapons than they have had in recent years along with a strong running game, but Walker represents a huge loss.