JACKSONVILLE, Fla. – Ask anyone in the Colts locker room about Daniel Jones, and the first thing they'll say about the quarterback is that he's tough and he's a good teammate.

He's proven that over the course of the last few weeks, playing through a fibula injury with no hesitation. He proved it even more on Sunday, during the Colts' game against the Jacksonville Jaguars, making the conscious effort to rejoin his teammates on the sidelines after leaving the game with an Achilles injury.

Jones sustained the injury late in the first quarter of the 36-19 loss, falling to the ground after throwing a pass and clutching his right lower leg (his left leg has the injured fibula). He tried to get up and walk to the sideline, but sat down grimacing as trainers rushed out.

After heading to the locker room, Jones was quickly ruled out with an Achilles injury, but returned to the sideline in the second half with a boot and an earpiece.

Prior to his injury, Jones had completed five passes for 60 yards and engineered a methodical touchdown drive ending in Jonathan Taylor's 18th touchdown of the season. It looked like he was just finding his rhythm when he sustained the injury.

"Daniel's the toughest guy that I've ever been around by far in my life," rookie quarterback Riley Leonard, who replaced Jones behind center, said after the game. "He's the most competitive person that I've ever met. So it's no surprise that he came back out there and cheered us on, and I remember going over to the sidelines and he was the first one to put the raincoat on me, first one to ask me what I see on that play and help me out and what to expect in certain situations. So it's just exactly who he is, whether he's playing or not. He's very consistent, win or loss, so I really respect that about him."

Head coach Shane Steichen said Jones' injury "didn't look good" and "could be season-ending," but he didn't have full clarity on the injury yet.

"Any time he can be out there — again, that's just him being a great teammate," Steichen said. "He has a huge injury. Some guys will sit in the locker room, he wants to be out there with his guys, and he went out there and showed support for Riley and the rest of the guys.

"I mean, the guy is as top notch as it gets. One of the best I've ever been around in a quarterback room — just his mentality, the way he goes about his business, the way he works, the way he treats people. Just phenomenal. Phenomenal."

Over the course of the season, Jones' demeanor and approach to the game has inspired a strong sense of unity in the Colts locker room and on the field – win or loss. That didn't change on Sunday, and it won't change now.

"He's our brother," offensive tackle Bernhard Raimann said. "He's giving it all for us, and we do the same for him. That's the kind of brotherhood you want and need in the locker room. And obviously we're praying for his quick recovery. But yeah, I would do anything for the guy. He's our quarterback. But Riley stepped in too, and he's a great guy too. He's been learning, he's been studying and we'll do whatever needs to be done to focus on the next games and win the next games."

"Just gotta find a way to keep fighting even though our leader went down," tight end Mo Alie-Cox said. "Things happen in football, definitely feel bad for Daniel, things like that. But as an offense, we gotta let something like that not affect us during the stretch of the game, obviously next man up mentality."

"We all in this thing together," defensive tackle Grover Stewart said. "He goes down, the next guy goes up. We all rally behind him. We all in this together."

Leonard earned praise from Steichen, Raimann and Michael Pittman Jr. – to name just a few – for his effort on Sunday, despite the loss. The rookie has worked closely and consistently with Jones throughout the season, breaking down film and learning everything he can from the veteran quarterback, and it's clear his teammates recognize the effort he's put in.

Leonard finished the game 18-of-29 for 145 yards and an interception, and scrambled for his first NFL touchdown at the end of the game. It was the rookie's first meaningful minutes in the NFL; he briefly appeared in the final minutes of the Colts' Week 8 blowout over the Tennessee Titans. But the Notre Dame grad didn't look flustered or unsure of himself at any point, despite playing through pouring rain and having some of his best throws called back due to penalties.

"I thought he went in and competed his tail off pretty darn good," Steichen said.

So, as the Colts begin adjust to this new normal with Leonard, they are confident that their young backup is going to do everything he possibly can to succeed. And in turn, they're ready to support him to the fullest extent possible.

"You see that he has talent, and the way he works, I think him and Dan are going to put in a lot of extra hours," Pittman said. "I think that's the great thing about Daniel, is that his season isn't over because he's hurt, and I think he's going to do everything he can to help him out."