The sophomore suffered the injury on a scramble. After falling hard on his right side, he left the field holding his right arm.
Garbers, who had 835 yards, seven touchdowns and two interceptions for 4-0 Cal entering the game, was replaced by Devon Modster.
The No. 15 Golden Bears were tied with ASU 7-7 at the half. Garbers completed 9 of 12 passes for 117 yards in the first half, including a 16-yard TD pass to Trevon Clark.