SAN DIEGO (AP) -- Brigham Young showed the effects of having already clinched the Mountain West Conference title in the first half against San Diego State.
Then the Cougars demonstrated why they are the class of the league by rebounding with a strong second half.
Freshman Harvey Unga ran for 161 yards and scored four touchdowns and Brigham Young (No. 19 BCS, No. 21 AP) routed San Diego State 48-27 on Saturday night.
Unga led a balanced offense that gained 538 yards, including 311 yards rushing. Unga scored on runs of 1, 7 and 3 yards, and caught an 8-yard TD pass from Max Hall as the Cougars (10-2, 8-0 Mountain West) completed the regular season with their ninth straight win.
BYU, a heavy favorite, led just 20-13 at halftime.
"A lot of people say that all the emotion from last week was going to take over and we were going to let up," said Unga about the Cougars' 17-10 win over Utah that clinched the outright title. Unga scored the game-winning touchdown against the Utes on an 11-yard run with 38 seconds left.
"We had a unique challenge this week in terms of focus," BYU coach Bronco Mendenhall said. "We handled it fantastically."
Winners of 16 consecutive conference games, the Cougars await their bowl fate. It appears likely that they will play in the Las Vegas Bowl, which can select any Mountain West team.
Unga and Fui Vakapuna (97 yards) carried the rushing load for BYU, which pounded the ball in the second half. The Cougars gained 324 total yards in the half, including 194 yards on the ground.
"It felt good handing off the ball, knowing they were going to get six, seven, eight yards every time they touched it," Hall said. "All the running opened up stuff through the air."
"For a young player like Unga to play with the poise and confidence that he plays with, I'm so impressed," Mendenhall said.
San Diego State (4-8, 3-5) allowed a combined 148 points and 1,902 total yards in its last three games, all losses.
"These last three games have been a little bit rough," acknowledged San Diego State coach Chuck Long, whose school has not had a winning season since 1998.
"[BYU] is very balanced and very physical," San Diego State linebacker Russell Allen said. "They have a system in place and they execute it."
San Diego State kept the game close, trailing just 20-13 at the break. But Unga scored on a 7-yard run on BYU's first possession of the second half.
Kevin O'Connell hit Lynell Hamilton with a 3-yard touchdown pass just past the midway point of the third quarter to pull the Aztecs to 27-20, but the Cougars responded with Unga's 3-yard TD run just before the end of the quarter.
Vakapuna scored from 2 yards out less than three minutes into the fourth quarter to give BYU a 41-20 lead.
O'Connell completed 33 of 55 passes for 288 yards and one interception. He also scored on runs of 7 and 2 yards.
The game was rescheduled from Oct. 27 due to wildfires in San Diego.
Running back Devontae Booker had 124 combined yards and a touchdown, and Utah spoiled Jim Harbaugh's Michigan coaching debut, beating the Wolverines 24-17 on Thursday night.
Arizona star linebacker Scooby Wright will have an MRI after injuring his left knee in the first quarter of the Wildcats' season-opening 42-32 win over UTSA on Thursday night.
Trevone Boykin threw for 246 yards and a touchdown and ran for 92 yards and another score to help No. 2 TCU outlast Minnesota 23-17 on Thursday night.
All-American defensive end Shawn Oakman and safety Orion Stewart have been suspended for Baylor's season opener Friday against SMU for a violation of team rules, a school spokesman told ESPN.com.
Ohio State quarterback Cardale Jones is "doing fine" after he was released from the hospital Wednesday night after being treated for symptoms related to a migraine headache.
East Carolina receiver Trevon Brown will miss three games after being placed on probation for a violation of the school's student code of conduct.