Saturday’s Cal-U.S.C. game has been delayed by Covid.

The University of California, Berkeley postponed its Saturday football game because of positive coronavirus cases among players, the school announced Tuesday evening. The matchup against the University of Southern California became the first game of the 2021 season at the sport’s top level to be rescheduled because of the virus.

Cal will instead host U.S.C. on Dec. 4, the school announced on Twitter.

Cal had played short-handed during its game last week, a loss to previously winless University of Arizona on Saturday. The Golden Bears were missing more than 24 players, including their starting quarterback, Chase Garbers, ESPN reported.

Cal, in a statement announcing Saturday’s postponement, cited “additional Cal football student-athletes who tested positive for Covid-19 and are unavailable to practice this week or play in the contest.”

“It was a difficult decision to postpone this Saturday’s game against U.S.C.,” Cal Athletic Director Jim Knowlton said. “We know how important every one of our games is to our student-athletes, especially our seniors who have been incredible representatives of the program, but it was the right thing to do.”

The Pac-12 Conference, which includes Cal, U.S.C. and Arizona, had reinstated its forfeit policy before the season after modifying it to stage the 2020 season amid the pandemic. As a result, games canceled because of virus outbreaks were more likely to be counted as forfeits instead of no contests.

Cal, in a statement before its game against Arizona, said 99 percent of football players were fully vaccinated. Students, faculty and staff are required to be vaccinated against Covid-19, though exemptions and accommodations were permitted in some cases. The city of Berkeley, Calif., has taken aggressive measures to control the virus, including requiring employees and customers at restaurants, clubs, bars and entertainment venues to be fully vaccinated.