Texas fired defensive coordinator Manny Diaz on Sunday, less than 24 hours after one of the worst defensive performances in the history of the program.

Coach Mack Brown announced that former Longhorns defensive coordinator and Syracuse coach Greg Robinson will take over the job.

“Our performance on defense last night was unacceptable, and we need to change that,” Brown said.

BYU ran for 550 yards, the most ever given up by Texas, in a 40-21 home victory on Saturday night. The performance put a potential breakthrough season on the brink of another big disappointment if the Longhorns can’t fix their defensive problems. Texas (1-1) plays No. 25 Mississippi (2-0) at home on Saturday.

Brown hired Diaz after Texas finished 5-7 in 2010 and defensive coordinator Will Muschamp left to be the head coach at Florida. The hire was a surprise considering Diaz had been defensive coordinator just one season at Mississippi State, but Brown called him a rising star in coaching who brought energy and new ideas to his struggling program.

Aside from a blowout loss to Oklahoma, Diaz’s first season was a success as Texas matured into the best defense in the Big 12. But the unit regressed into one of the worst in program history in 2012. As the season wore on, players complained that teammates weren’t lining up correctly or playing hard every game.

●USC STRUGGLING: Fans in cardinal-colored jerseys leaned over the railing and bellowed their boos into the Coliseum tunnel. Negative chants rained down on the coach as he ran to the locker room after each half.

Only Southern California’s fans weren’t booing the opposition in the Trojans’ home opener. They’re already fed up with Coach Lane Kiffin and a night of historical ineptitude by his offense.

Andrew Furney kicked a 41-yard field goal with 3 minutes 3 seconds to play as Washington State beat then-No. 25 USC, 10-7, late Saturday night for its first victory at the Coliseum in 13 years.

Kiffin’s two-quarterback offense managed 193 yards on 63 plays, with no pass completion longer than eight yards.

“You can’t worry about that,” Kiffin said of the chants. “I think I heard those before the game started, during warm-ups, so I’m used to it.”

●GAFFNEY LEADS CARDINAL : With school rushing leader Stepfan Taylor in the NFL, Tyler Gaffney made sure defending Rose Bowl and Pacific-12 champion Stanford’s ground game kept going strong.

In a 34-13 victory over San Jose State, he ran for 104 yards and two touchdowns in his first game back after playing baseball in the minors last year. Stanford (1-0) is ranked No. 5.