SANTA CLARA -- The 49ers will elevate quarterback Nick Mullens from the practice squad to serve as C.J. Beathard’s backup after Jimmy Garoppolo sustained a season-ending knee injury Sunday.

The 49ers also will bring in a group of free-agent quarterbacks to work out Tuesday, coach Kyle Shanahan said Monday.

“I know we’re working out a number of guys tomorrow,” Shanahan said. “Right now, our plan is bring Nick up, so we have two right away.”

The group of quarterbacks expected to work out for the 49ers includes veteran free agents Kellen Clemens, T.J. Yates and Tom Savage. Shanahan said the team also has reached out to Matt Moore, but the coach said he wasn't sure if the QB would attend the workout.

One player who will not be at the workout is Colin Kaepernick, Shanahan said. He said the team hasn't discussed Kaepernick this year after he was a subject of conversations a year ago.

“I made that decision [to not pursue Kaepernick] because of the style of offense we wanted to go with,” Shanahan said. “That’s kind of what I said last year. It’s the same situation now. I always look into what style of offense I want to do, what style of offense we’ve been doing for the last two years.

“When you start to get to these quarterbacks we’re talking about, C.J.’s our guy, and we have Nick Mullens backing him up. When you get into a third or fourth guy, whoever that is, you’d like to bring in guys who you felt you didn’t have to change much of your offense for.”

Garoppolo is scheduled to undergo surgery to repair his torn ACL at some point in the next week or two after the swelling in his left knee goes down. Shanahan said he wasn't aware of any additional damage to Garoppolo’s knee.

Clemens, 35, is a 12-year NFL veteran who has started 21 of his 64 career games during his career with the New York Jets, St. Louis Rams and the Chargers. He has 16 career touchdown passes and 21 interceptions.

Yates, 31, started 10 of the 20 games in which he appeared with the Houston Texans, Atlanta Falcons and Miami Dolphins. He has 10 TD passes and 11 interceptions.

Savage, 28, has started nine of his 13 games with the Texans. He has thrown five TD passes and seven interceptions.

Moore, 34, is a 10-year pro who has 30 career starts in his 49 appearances with the Carolina Panthers and Dolphins. He has thrown 45 TD passes and 31 interceptions.

Click to watch Shanahan's full press conference