Jimmy Garoppolo’s crash course in Kyle Shanahan’s playbook this week went well enough the 49ers will deploy him as C.J. Beathard’s backup Sunday against the Arizona Cardinals, Shanahan confirmed Friday. Garoppolo, acquired in a Tuesday trade with the New England Patriots, is expected to assume the starter role at some point this season. If not next game against the New York Giants, it could happen after the bye week when the 49ers host the Seattle Seahawks on Nov. 12. Shanahan maintained there is no set date for Garoppolo to start. But Sunday’s role will be as an emergency backup. “He’s worked real hard at it, gotten more comfortable each day,” Shanahan said. “Definitely not there yet, but if that situation presents itself, we’ll have a plan to go with him so he can function.” The 49ers will not summon undrafted rookie Nick Mullens from the practice squad as another backup, Shanahan said.