STANFORD, Calif. -- No. 21 Stanford was the winner in two games Saturday.

Stanford quarterback K.J. Costello threw four touchdown passes and running back Bryce Love rushed for 125 yards to lead the Cardinal to a 38-20 victory over No. 8 Notre Dame.

More important to the Cardinal (9-3) was the game 700 miles away in Seattle, where Washington beat Washington State, giving Stanford a berth in next Friday's Pac-12 championship game against USC in nearby Santa Clara, Calif.

The Cardinal and Washington wound up tied for the Pac-12 North title with 7-2 records. But Stanford gets the nod for the title game based on its head-to-head victory over the Huskies. Washington State would have been the Pac-12 North representative in the conference championship game if it had beaten Washington.

Even though the score of the Washington game was announced at regular intervals at Stanford, Cardinal players insisted they didn't know that result until after their game.

"I had no idea until postgame," said Costello, who completed 14 of 22 passes for 176 yards, the four scores and no interceptions. "I had heard it was 20-zip or something, and I saw a lot of smiling faces so I figured that was a good sign."

Costello, a redshirt freshman, made just his fifth career start on Saturday and had his best game.

"I can't say enough about this kid's ceiling," Stanford coach David Shaw said. "I'm really excited about where he's going."

Costello was not the Cardinal starter when Stanford lost to USC 42-24 in the second game of the season.

"To go from 1-2 to winning eight of our last nine games and get back to the Pac-12 championship game says a lot about our players," Shaw said. "Now we have six days to get ready for a good team that is on a bye."

The game at Stanford meant more to the Irish, who seemed to be in line for a berth in one of the four major bowls not included in the College Football Playoffs (Orange, Fiesta, Cotton, Peach).

Now, with a 9-3 record and mediocre performances in the final three games, that is in question.

Three Notre Dame turnovers, all in the fourth quarter, ruined the Fighting Irish's chances against Stanford.

"Each game we've lost we turned the football over against good teams," Notre Dame coach Brian Kelly said, "and you can't turn the ball over against good teams."

The Irish were ranked No. 3 in the CFP rankings two weeks ago before committing four turnovers in a 41-8 loss to Miami. They had another turnover in their tougher-than-expected 24-17 home win against Navy last week.

Irish quarterback Brandon Wimbush threw touchdown passes of 83 and 75 yards, but he was 9 of 26 for 91 yards and two interceptions otherwise. Notre Dame running back Josh Adams, who entered the game needing 100 yards to match the school's single-season rushing mark, was limited to 49 yards on 20 carries.

Notre Dame held a 20-17 lead entering the fourth quarter, but it all fell apart for the Irish in a span of 3:36.

Costello's 20-yard scoring pass to Kaden Smith early in the fourth quarter put the Cardinal ahead to stay at 24-20.

An interception by Stanford's Curtis Robinson at the Notre Dame 35 on the Irish's next possession led to Costello's 12-yard touchdown pass to Dalton Schultz, increasing the Cardinal's lead to 31-20. Then a fumble by C.J. Sanders on the ensuing kickoff gave Stanford the ball back on the Irish 18, and Cameron Scarlett cashed that in with a 3-yard scoring run that made it 38-20.

"We turned a good game into a not-so-good game with turnovers late," Kelly said. "It was going to go down to the last possession if we didn't give them two touchdowns."

The other issue for Stanford was Love's health. Bothered by sprained ankles over the second half of the season, he said he felt good after Saturday's game.

"His pain tolerance is unbelievable," Shaw said.

Love had 94 of his yards in the second half.

"We might have played our best game," Shaw said. "Not perfect, but in all phases it may have been our best game."

NOTES: Notre Dame RB Josh Adams began the day with 1,337 rushing yards, 100 shy of the school record set by Vagas Ferguson in 1979. ... Irish WR Equanimeous St. Brown, who was listed as questionable after suffering a concussion last week, was in the starting lineup. His 75-yard touchdown reception on the first play of the second half gave Notre Dame a 17-14 lead. ... Stanford LB Joey Alfieri left the game in the first quarter with an apparent right arm or shoulder injury. ... Stanford RB Bryce Love has 1,848 rushing yards, 41 shy of Toby Gerhart's 2009 mark for the school's second-best single-season total. Christian McCaffrey set the record with 2,019 yards in 2015.