Mariota broke his right leg in a 38-17 loss at Jacksonville on Saturday, a crushing setback for a team that had so many things go right while winning three in a row and seven of 10 previously.
"That breaks my heart, man," Titans offensive tackle Taylor Lewan said. "Love him. That guy's an awesome dude. For that to happen to him, it's unfair."
A few hours later, the Titans (8-7) were eliminated from playoff contention when Houston beat Cincinnati to win the AFC South for the second straight season.
Tennessee needed the Bengals to win to set up an AFC South title game next week against the Texans. Instead, coach Mike Mularkey's team will play a meaningless home finale - without their star QB.
With the Titans trailing 25-10 late in the third quarter, Mariota was carted off the field with an air cast on his fractured fibula. Rookie Sheldon Day sacked Mariota as he scrambled on first down and grabbed him around the lower legs. Mariota signaled to the sideline as he pounded the ground. Trainers rushed to his side, put on the air cast and lifted Mariota onto a cart. Teammates and even some Jaguars patted Mariota on the shoulders before he excited.
"We didn't protect him - offensive line, running backs - we didn't protect him all day," Titans running back DeMarco Murray said.
Mariota was hurried early and often, leading to errant throws all over the field. He completed 8 of 20 passes for 99 yards, with a touchdown and two sacks.
The Jaguars (3-12) played inspired football, partly because popular coach Gus Bradley was fired six days earlier and partly because the Titans embarrassed them on national television in late October. Mariota was a prime target, along with Murray and fellow running back Derrick Henry.
"It's the first time this season we have been beaten like that," said Mularkey, who estimated Mariota is facing at least six weeks of recovery time. "It's a bad time for it."
Journeyman Matt Cassel replaced Mariota and completed 13 of 24 passes for 124 yards, with a touchdown and an interception. His 14-yard score to Delanie Walker made it 25-17 in the fourth quarter, but Jacksonville answered on the ensuing drive and then sealed the victory when rookie Jalen Ramsey returned an interception 30 yards for a score.
Cassel will be the starter for the finale, Mularkey said.
"Cassel is a guy who's been around a long time and has won a lot of games," Murray said. "He's the next guy up and he prepares every single day, every single week like he's the starter, so I know he'll be ready to play."
Maybe, but he's unlikely to give the Titans the same passing-running combination Mariota did.
The second overall pick in the 2015 NFL draft, Mariota completed 61.2 percent of his passes this season for 3,426 yards with 26 touchdown passes and nine interceptions. He also ran for two scores.
Although he hadn't thrown a TD pass in two straight games entering Saturday, he threw at least two in a franchise-record eight straight before that. His 107.2 passer rating over the previous 11 weeks was third behind Atlanta's Matt Ryan and New England's Tom Brady during that span.
"I think everybody to a man went to see him in the training room and wished him well," Cassel said.
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