Texas' new defensive coordinator Manny Diaz looks on before the Texas Orange and White spring football scrimmage on April 3, 2011, in Austin, Texas. The Orange team won 27-7. (AP Photo/Michael Thomas)

BYU not only thumped Texas out of the AP Top 25, but its huge offensive effort left the Longhorns defensive coordinator out on the street.

Following one of the worst Texas defensive performances in school history, head coach Mack Brown fired his defense coordinator Manny Diaz.

The Cougars rushed for an unbelievable 550 yards in their Saturday 40-21 victory over Texas. Quarterback Taysom Hill had a game-high 259 rushing yards, and running back Jamaal Williams was right behind him with 182 yards. The Texas defense allowed nearly eight yards per rush.

Brown knew the defense fielded Saturday would only lead to another underachieving year, which led to his ultimate decision.

“Our performance on defense last night was unacceptable, and we need to change that,” Brown told the Associated Press.

Brown hired Diaz as Longhorns defensive coordinator in 2010, when Will Muschamp accepted a head coaching position at Florida, with hopes he would be a positive change to the program's defense, according to the Associated Press report.

Brown expressed enthusiasm at that time for Diaz's ideas and energy. Three years later, Diaz failed to make effective changes in the Texas defense, hence the 40-21 loss and Diaz's reassignment.

Now the Texas head coach is facing the heat, and ESPN's Mark Schlabach said Brown could be out as fast as Diaz if he doesn't get the program's defensive struggles worked out soon.

Whitney O'Bannon is a new media sports writer for the Deseret News. Follow on Twitter at @whitney_oban.