Colorado star safety Shilo Sanders is doubtful for Saturday's game against No. 8 USC and is not expected to play, sources told ESPN, leaving a struggling Buffaloes secondary even more vulnerable against the Trojans.

Sanders did not practice this week, sources said, and is slated to be replaced in the starting lineup by Southern Utah transfer Rodrick Ward. Coach Deion Sanders said on his radio show this week that his son had a kidney injury that was causing him to urinate blood.

Sanders is a graduate student who played at South Carolina and Jackson State before starting at Colorado this season. He has been one of Colorado's defensive linchpins, with 26 tackles this season while forcing a fumble and recording an 80-yard interception return in the victory over Colorado State.

The expected loss of Sanders leaves Colorado without two of its most valuable players, as Travis Hunter (333 snaps at WR/DB) and Sanders (312) are among the team's top three players in total snaps. Coincidentally, both have kidney issues.

Hunter, the lockdown cornerback who moonlights at receiver, is out multiple weeks after taking an illegal hit from Colorado State's Henry Blackburn.

That leaves Colorado short-handed against returning Heisman winner Caleb Williams and a USC passing offense that ranks No. 3 nationally with 377.2 yards per game. Williams will be squaring off in a quarterback duel with Sanders' brother, Shedeur, in a game that's intriguing enough to NFL front offices that 30 scouts from 21 teams will be in attendance.

Colorado's pass defense ranks No. 111 nationally, yielding 269.2 yards per game. USC is No. 68 at 228 yards per game.

The expected start at safety will be a big test for Ward, a backup who has nine defensive snaps, 57 special teams snaps and three tackles this year behind Shilo Sanders on the depth chart. Sanders is one of Colorado's vocal leaders and key figures in the secondary.

According to ESPN Stats & Information, Ward has dropped into coverage on three snaps this year and wasn't targeted as a primary defender.

Colorado is likely to have leading wide receiver Xavier Weaver, who is considered probable to play, sources said. Weaver suffered an unspecified injury in last week's loss to Oregon.