Jabari Bird sustained what appeared to be a fairly sharp turn of his right ankle with 5:02 left in the first half at Creighton.
Bird writhed on the floor after coming down awkwardly on his ankle, then was helped off the floor.
A couple minutes later, the freshman guard had his ankle wrapped in ice on the Cal bench.
Creighton finished the first half with a 10-1 run and leads 30-19 at the break.
Cal shot 33 percent in the first half, turned the ball over seven times and was outrebounded 22-15.