"I always knew he was going to be a great player. I watched some of his highlights when we drafted him,'' Walker said of Mariota, who won the Heisman Trophy at Oregon. "When I met him he was quiet. Most of the time the quiet guys are always the good players. He didn't really talk much about his game, and I respect him for that."
Mariota's rookie season is now officially over.
Interim coach Mike Mularkey made the announcement after practice on Wednesday at Saint Thomas Sports Park. Second-year quarterback Zach Mettenberger will start Sunday's season finale against the Colts.
Mularkey said Mariota's rookie season will go down as a success.
In his 12 starts, Mariota completed 230-of-370 (62.2%) passes for 2,818 yards, with 19 touchdowns and 10 interceptions. His final passer rating: 91.5.
Mariota, the second overall pick of the NFL Draft, broke several franchise rookie records, including most touchdowns (19), completions (230), passing yards (2,818) and passing attempts (370). Mariota completed three or more touchdown passes on four different occasions during his rookie season. He joined Peyton Manning (four in 1998) as the only rookie to accomplish the feat.
"I think he's progressed very well,'' Mularkey said of Mariota. "I wish things were different where he didn't get hurt earlier in the year. I think the end of the year might have even been better because he was slowed with the injury.
"But as far as his progress, I thought he made great strides. He learned a lot, went through a lot, saw a lot. A lot of the teams (we've played) are playoff caliber teams at the end and the defenses we've faced, the fronts, the blitzes, the things we saw, he saw, and that will benefit him for this next year easily."
Heading into Sunday's game against the Colts, the Titans didn't want to put their injured star in harm's way.
Mariota injured his right knee during the second quarter of the team's December 20 game against the Patriots when he was sacked by linebacker Jamie Collins.
Mettenberger replaced Mariota on the next series, and finished the 33-16 loss to the Patriots. Mettenberger also started for the Titans in Sunday's 34-6 loss to the Texans.
Earlier in the week, Mularkey said Mariota did some drop backs, but he indicated the Titans wouldn't play him unless he was 100 percent. The Titans ultimately decided the best route would be to hold Mariota out of the finale.
"This was the third day (of him working out) and we're going to rule him out," Mularkey said of Mariota. "He's not as far along as we thought he'd be by today and it's not worth the risk.
"He'd play if he could. But it's doing it the right way, being smart about it."
Walker said a lot of things stood about Mariota during his rookie season, including his attitude.
"His attitude, his toughness, the way he prepared for the game,'' Walker said. "I always thought he went in there and played the best he could. He is a very confident guy and knew what he was supposed to do."
Mariota missed two games earlier this season after suffering an MCL sprain in his left knee in the team's October 18 game against the Dolphins. Mariota had four games with at least three touchdown passes this season, tying Peyton Manning (1998) for the most ever by an NFL rookie.
Receiver Dorial Green-Beckham said Mariota proved a lot during his rookie season.
"It's extremely hard to do what he did, but he handled it,'' Green-Beckham said. "The smartest thing right now is to not let his injury get any worse, so he'd get set back.
"Marcus had a great rookie year, and he's just going to keep getting better. Fans should be excited about what he's going to do in Year Two."