KANSAS CITY, Mo. -- After Sunday's loss to the Kansas City Chiefs, as San Francisco 49ers coach Kyle Shanahan was telling reporters that there's a "fear" that starting quarterback Jimmy Garoppolo suffered a season-ending ACL tear, which was confirmed Monday, backup C.J. Beathard was in the team's training room visiting with Garoppolo.

Beathard's message to Garoppolo was one of love and appreciation. Garoppolo's response was simultaneously telling of his health status and encouraging for Beathard.

"He told me to lead these guys," Beathard said.

The 49ers fear a season-ending injury for Jimmy Garoppolo. Peter Aiken/Getty Images

It's a job to which Beathard is already accustomed, even though he's only three games into his second NFL season.

Last year, Beathard arrived as a third-round pick out of Iowa and his job was to provide insurance for veteran Brian Hoyer. Hoyer struggled early in the season and Beathard replaced him in Week 6 against the Washington Redskins. Beathard would go on to start the next five games, even leading the Niners to the first victory of the Shanahan regime in Week 10 against the New York Giants.

As coincidence would have it, Beathard suffered knee and hip injuries in Week 12, opening the door for Garoppolo to take over. From there, Garoppolo won the final five games of the season, signed a $137.5 million contract and became the face of the franchise.

Asked if he would look for a veteran quarterback, Shanahan said he believes in Beathard and indicated that any quarterback brought in would be to back up Beathard.

Moments after revealing the possibility of an ACL injury for Garoppolo, Shanahan quickly pivoted to expressing his optimism about Beathard.

"I have got a lot of confidence in C.J.," Shanahan said. "... He came in today, made a hell of a throw on that fourth down. No hesitation. C.J. is a gamer. Everyone in here has a ton of respect for C.J., how he handles himself. He’s a man out there and he’s a very good quarterback and we’re fortunate to have him."

The good news for the Niners is that this won't be Beathard's first time stepping into a difficult situation. The 49ers were 0-6 when he started his first game as a rookie and the season was already mostly lost.

C.J. Beathard appeared in six games as a rookie last season. AP Photo/Marcio Jose Sanchez

While Beathard's numbers -- 1,430 yards with four touchdowns and six interceptions and a passer rating of 69.2 -- weren't impressive, he won over teammates and coaches with his toughness and willingness to stand in the pocket and fire passes as he took hits from all angles.

"It’s huge having already played last year," Beathard said. "I feel like it will really help me going forward having had the experience. ... I think it will be a little bit easier this time."

In the offseason, even as the Niners were committing to Garoppolo, Beathard ventured to Nashville with teammates George Kittle and Trent Taylor and a few other NFL players to train. That group spent time working on routes and dived deeper into Shanahan's playbook. Kittle, who played with Beathard at Iowa and is one of his closest friends, said he saw a lot of improvement in Beathard during that time.

"I’m not worried at all about C.J.," Kittle said. "He’s a hell of a quarterback. He knows how to win. So I’m not worried about that at all. He’s going to step right in and he’s going to do just fine.

"Coach Shanahan has the highest standards for every single person on the team, especially C.J. That’s why they took him in the third round, they thought so highly of him. And he did his job last year and he’s going to step up and do it again no matter what happens."

Of course, this second turn as the starter also comes with far more in the way of expectations. When Beathard took over a winless outfit in 2017, there weren't many delusions of grandeur as he stepped in for career journeyman Hoyer.

This time, there's still a whopping 13 games left to play and he's replacing Garoppolo, one of the most intriguing young quarterbacks in the league. To put it bluntly, the Niners' season now rides on whether Beathard can, at least, provide some of the things Garoppolo brings to the table.

The first order of business, according to Beathard, is to do exactly what Garoppolo told him in the training room.

"It’s just a matter of keeping everybody in it and staying positive," Beathard said. "There’s going to be every opportunity in the world for guys to be mad or down about certain things but we’ve got to keep our morale and stay positive and move on to next week."