"He had a family situation that he's got to go take care of," Shaw said. "He's in our thoughts and prayers. He's OK. But he'll be with his family this week. We hope to get him back soon."
Speaking to reporters after practice Tuesday, Shaw said that Yankey, a consensus All-American last year, is healthy and in good standing with the team. The 6-foot-5, 313-pound senior, who won the Pac-12's Morris Trophy last year for the top offensive lineman, is from Roswell, Ga.
Sophomore Josh Garnett will start in place of Yankey at left guard.
"We'll rally around him in spirit, but we're going to go out and try to win a game without him," Shaw said.
The No. 5 Cardinal (3-0, 1-0 Pac-12) face the Cougars (3-1, 1-0) at Seattle's CenturyLink Field on Saturday.
Shaw did not specify how long Yankey would be gone, and a release from the school said they would inform the media when he would be able to return.