The Pac-12 apologized to the Stanford football team Friday after an inconclusive COVID-19 test led to multiple players, including starting quarterback Davis Mills, missing the Cardinal's season-opening loss to Oregon on Saturday.

"During Pac-12 game day testing this past Saturday, there were testing protocol errors with respect to a Stanford student-athlete who tested positive for COVID-19," the Pac-12 said in a statement. "The student-athlete and others who were immediately identified as individuals who would be high-risk contacts if the student-athlete were positive did not play in the game, in accordance with Pac-12 protocols, and the student-athletes were immediately isolated."

The player who received the inconclusive test was Mills, according to a conference source.

Stanford, without naming Mills, said the player who received the inconclusive test has repeatedly tested negative for COVID-19 using PCR tests since returning to campus.

On Saturday, less than two hours before kickoff, Stanford announced that defensive end Trey LaBounty, wide receiver Connor Wedington and Mills would be unavailable due to "test results and contact tracing protocols." A fourth player was also placed into quarantine after being designated as a close contact through Santa Clara County and Stanford's contact tracing protocols.

All four players will be available to play against Colorado on Saturday.

"We apologize to the Stanford football team and its supporters, and especially to the student-athletes who were held out of the game as a result of the testing protocol errors," the conference said. "We are working with our game day testing partner to ensure this type of error does not occur in the future."

With Mills sidelined, Stanford lost 35-14. Quarterbacks Jack West and Tanner McKee combined to complete 16 of 26 passes for 216 yards.