JACKSONVILLE, Fla. -- Tennessee Titans quarterback Marcus Mariota started the day as the backup against the Jacksonville Jaguars because of an elbow injury that affected his ability to feel and grip the football.

There were rumblings on social media about Mariota's toughness, because he missed the home opener and didn't start against the Jaguars.

Head coach Mike Vrabel firmly stood up for his quarterback after Mariota led Tennessee to a 9-6 win, handing Jacksonville its first loss of the season.

"You're injured. That doesn't have anything to do with his toughness," Vrabel said. "When he pulls a ball and goes north and south on that defense, I wouldn't question his toughness. Those guys are big; they are fast. It's a good football team, they play aggressive and have a lot of good football players over there. I wouldn't question his toughness."

Mariota was rushed into duty in the first quarter after starter Blaine Gabbert was knocked out of the game with a concussion. There was a sense of calmness when Mariota got to the huddle. Wide receiver Corey Davis said Mariota didn't say much, but he gave off aura of confidence and poise as he called the play.

Added left tackle Taylor Lewan, "He's a stud. When Marcus comes in you, don't think, 'Aw man, he's hurt.' You think, 'Good. Marcus is in; our quarterback is here!'"

It took a little bit for Mariota to get going. He completed only three of his seven passes in the first half, although three of them were dropped by Titans wide receivers.

Despite not being effective through the air, Mariota showed that he can still do damage with his legs by gaining 51 yards on seven rushes, including a 13-yard gain from Tennessee's 4 in the first quarter. It gave the best defense in the NFL something else to consider.

The coaching staff talked with Mariota as the game went on to get a feel for what he was comfortable with. Offensive coordinator Matt LaFleur mixed in some old-fashioned runs on consecutive plays and also presented some spread concepts. The variety of plays kept the Jaguars off balance.

Mariota settled into a rhythm in the third quarter, completing 3 of 5 passes leading to a 36-yard field goal by Ryan Succop. LaFleur had confidence in Mariota's ability to push the ball down the field as shown by a call that gave the quarterback a chance to throw it deep to Davis on the first play of the second half.

Later in the game, Mariota threaded a pass to Davis on a crossing route for 12 yards on third-and-5 from the Jaguars' 43, which set up Succop for the winning field goal.

The Titans held off the Jaguars thanks to a late run by Mariota. Vrabel showed courage by allowing LaFleur to call a read-option play on third-and-1 at the Tennessee 33 with 2:31 left and the Jaguars down to their final timeout. It was a bold move considering Mariota was dealing with the injured elbow. The gutsy call worked, as Mariota read the defense and kept the ball rather than handing it off and broke a 15-yard run.

"He's a dog," Davis said of Mariota. "That says a lot about him to go out there and play hurt. It's not easy to do, but he did it. Ocho is a great competitor, and we love him."

The play was a key part of a courageous relief effort that led to Mariota's getting the game ball in the locker room after an invaluable road win. Vrable summed up Mariota's effort in one word:

"Fantastic," he said. "It was cool for me to give Marcus the game ball in the locker room. He cares about this team immensely. You saw him come in and give us a spark and give us some third-down conversions to seal the deal for us late in the game."

Although it was Mariota who gave the Titans a spark, he credited the defense for holding Jacksonville to only six points. Now Tennessee's attention turns to a clash with the Philadelphia Eagles.