"It's 50-50 at best even if he's cleared and probably leaning more toward not," Helton said.
Daniels, a true freshman, was allowed to throw on Thursday, Helton said, but has not been medically cleared for contact since suffering a concussion against Utah last Saturday.
Helton will receive an update Friday from the team's medical staff but did not indicate when he'll officially settle on a starter.
Sears, who succeeded former USC star Sam Darnold in high school, competed with both Daniels and Fink in training camp before landing at third on the depth chart. He has not attempted a pass at the college level.