While not the way Neuheisel had planned, that decision was made easier after he found out Cowan will undergo surgery on the ACL in his left knee and will miss the entire season, according to L.A.-area media reports.
"All I know is I need the surgery and I'm not going to be able to play next season," Cowan told reporters Saturday.
Olson's injury, which will require doctors to put a screw into his foot to help it heal, will keep him out six to eight weeks.
In practice Thursday, Cowan and Olson went down on back-to-back plays. Both were wearing helmets, shoulder pads and shorts, in the next-to-last practice of an injury-free spring.
Cowan, who won the starting QB job in spring practice, has already used up his redshirt eligibility, was unsure of his future plans.
"I don't know," Cowan told reporters. "I wasn't expecting this. There are a lot of things that can happen at this point. I need some time to think about what's going to happen."
Olson and junior college transfer Kevin Craft will compete for the starting job.
"We're going to play that position well," Neuheisel said. "I have full confidence in [offensive coordinator] Norm Chow. I have full confidence in the kids to give everything they've got."
ESPN's Ivan Maisel and information from The Associated Press contributed to this report.