SANTA CLARA -- The 49ers will have a different starting quarterback and a new backup on Sunday against the Los Angeles Chargers.

Only the identity of the 49ers’ No. 3 quarterback will not change after Jimmy Garoppolo’s season-ending injury.

The team's emergency quarterback is still Kyle Juszczyk, whose day job is being the 49ers’ starting fullback.

Because the 49ers have not carried a true third quarterback for any game the past two seasons, Juszczyk is the man who remains in the emergency role.

“Last week when Jimmy got hurt, it flashed in my head a little,” Juszczyk said of the possibility of getting in a game at quarterback. “But, honestly, there’s comfort in knowing that not much is expected from me. I’m sure it would be a very basic package. I’m sure I’d be handing the ball off, mostly. And if I did throw, it would be mostly three-step sorts of things.”

Head coach Kyle Shanahan said he has never been forced to go with the emergency fill-in during his NFL coaching career. And Juszczyk, who was also Baltimore’s emergency quarterback during his first four pro seasons, has never taken a snap at the position in an NFL game.

Juszczyk played many positions in high school, including quarterback, which makes him the most-qualified candidate to step in if the team's top two quarterbacks became unavailable. He also ran some wildcat plays at Harvard, where he was a three-time All-Ivy League selection as a tight end.

Juszczyk said he sets aside some time every Friday to take snaps on the side from 49ers center Weston Richburg. Juszczyk even ran a play from quarterback for the first time this season during the team’s walk-through on Friday, he said.

The 49ers would have counted on running back Jerick McKinnon to be the emergency quarterback, based on his play at that position during his college days at Georgia Southern, Shanahan said. But McKinnon sustained a season-ending knee injury eight days before the team’s season opener, which cleared the way for Juszczyk to again fill that role. But even if McKinnon were healthy, Juszczyk was not ready to hand him the job.

“’Jet’ threw, like, one pass a game in college,” Juszczyk quipped. “People think he was a quarterback, but he really wasn’t.”

(Fact check: McKinnon completed 34 of 81 pass attempts for 829 yards with 12 touchdowns and four interceptions during his college career.)

The 49ers appear set with C.J. Beathard and Nick Mullens as the team’s top two quarterbacks. At some point, the club would like to add a quarterback to develop on the practice squad. But, regardless, Juszczyk will continue to fill the role of the No. 3 spot.

“Hopefully, it doesn’t come to that,” Juszczyk said. “But if it does, I’m going to have a great time.”