Nick Mullens would be in line to start for the 49ers if Beathard can't go. Beathard was forced into action in Week 3, when 49ers starter Jimmy Garoppolo left a loss against the Kansas City Chiefs in the final minutes after suffering a season-ending torn ACL.
Mullens, 23, has never thrown a pass in the NFL. The Southern Mississippi product completed 72.1 percent of his throws for 396 yards, one score and three interceptions in four 2018 preseason games. He also ran for two scores. Mullens threw for 11,994 yards, 87 scores and 46 interceptions in 44 collegiate contests.
Niners coach Kyle Shanahan told reporters Tuesday that Beathard would play if his team was playing on Sunday. He also said the 49ers probably wouldn't know if Beathard will play until he tested out the wrist on Thursday. Shanahan said Mullens is "as ready as you can be."
"Nick works his tail off whether he was on practice squad all last year, some of this year, since he's been the two," Shanahan said. "Nick's a very smart guy who works at it nonstop. He'll be able to go in there and execute the offense and knows what he's doing."
Beathard suffered the wrist injury by hitting it on a helmet in the second quarter in the 49ers' Week 8 loss to the Arizona Cardinals.