Jimmy Garoppolo will serve as the 49ers' No. 2 quarterback on Sunday against the Arizona Cardinals, an indication that the team's recent acquisition is picking up the offense at a quick pace.
Kyle Shanahan said on Friday that the plan was to monitor Garoppolo's grasp of the offense during the week, and if they felt it was coming along slowly, to elevate rookie Nick Mullens from the practice squad to be C.J. Beathard's backup against the Cardinals.
"We were going to wait on that all week," Shanahan said. "If we felt that if (Garoppolo) couldn't go in and function, then we'd have pulled Nick up.