The Southern California Trojans spent the first two weeks of the season pulling out improbable wins, then cruised to a comparatively easy victory in their third game.

Now No. 19 USC (3-0, 3-0 Pac-12) faces maybe its toughest matchup when it hosts the Colorado Buffaloes on Saturday afternoon. Butthere remains a possibility of the game being postponed due to COVID-19 issues.

The Trojans had a player test positive following last week's win at Utah in what was the first positive test for USC this season. The football program released a statement on Tuesday saying it was informed of the positive test Monday night and that the player was symptomatic and had been quarantined. The unnamed player had tested negative four times in a 36-hour span before traveling to Utah with the team, and tested negative on game day.

USC closed its practice facilities and conducted all team business virtually while awaiting results from another round of testing on Tuesday afternoon, multiple outlets reported.

Colorado (2-0, 2-0) already had an unplanned bye week when its game against Arizona State last week was canceled due to a coronavirus outbreak with the Sun Devils. The Buffaloes have a chance to start 3-0 in the Pac-12 for the first time since joining the conference.

"There's a lot of ramifications about this game," first-year coach Karl Dorrell said. "It's a shortened season and we're just trying to maximize our chances. We're hoping to be a factor in this thing. That was our goal in the very beginning, to be in the thick of it when the games mattered most."

Colorado built some momentum with impressive wins against UCLA and at Stanford to open the season. Quarterback Sam Noyer has had a strong debut, throwing for 512 yards and three touchdowns against one interception. He has also rushed for three touchdowns.

Noyer's favorite target has been Dimitri Stanley, who has 12 receptions for 192 yards and a touchdown.

Running back Jarek Broussard has also made an impact, averaging 154 yards on the ground over the first two games to go with three scores. He burst onto the scene with a 187-yard performance in a 48-42 win over the Bruins.

To start 3-0, the Buffaloes will have to go against a Trojan defense that forced five turnovers against the Utes and held Utah to 3-for-11 on third down conversions.

USC might be without two of its top running backs. Markese Stepp (pectoral strain) didn't play against the Utes and Stephen Carr (neck) was limited after taking a knee to the helmet. Vavae Malepeai ran for 62 yards and a score. Sophomore Kenan Christon made the most of his opportunity with 55 yards on the ground, 47 on one play.

Christon could see more action if Stepp and Carr can't go.

"One of his areas of growth, which he works extremely hard on, is pass protection and making that a strength for him, but he's going to gain more opportunities," Trojans coach Clay Helton said. "Obviously, we have a wealth of talent at the position."