San Francisco 49ers quarterback C.J. Beathard is uncertain to play Thursday night against the Oakland Raiders due to a right (throwing) wrist injury, head coach Kyle Shanahan said Tuesday.”C.J. would be good if we were playing on Sunday,” Shanahan said. “But, it’s going to be a test for Thursday, and probably won’t know until then.”Beathard didn’t miss a snap against the Arizona Cardinals last week, going 14 for 28 for 190 yards and a touchdown while taking four sacks and eight QB hits, but Shanahan said the QB’s wrist hurts and he’s “struggling today to hold a ball.”Second-year undrafted free agent Nick Mullens would start if Beathard can’t go, and Tom Savage would serve as the backup.Shanahan said Mullens, who spent a year-plus on the practice squad until being elevated to the active roster as the backup after Jimmy Garoppolo’s season-ending injury, is “as ready as you can be” if the Southern Miss product is forced into his first NFL game.”Nick works his tail off, whether he was on practice squad all last year, some of this year, since he’s been the (backup),” 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 has gone 0-5 as a starter this year after going 1-4 last year. He has 1,252 yards, eight touchdowns and seven interceptions in five-plus games since relieving the injured Garoppolo late in Week 3.Savage, who has been on and off the 49ers’ roster, spent much of this year as a free agent after failing to make the New Orleans Saints’ roster out of training camp. He went 2-7 in nine starts for the Houston Texans over the previous two years.