"I am very excited Manny Diaz is joining our staff," Bulldogs coach Skip Holtz said Tuesday in a release. "He brings great experiences with a lot of success at a lot of different stops. He brings excitement, a passion for the game, plenty of experience and a reputation for success that precedes him."
Diaz was fired by then-coach Mack Brown and replaced by Greg Robinson after the Longhorns gave up 550 rushing yards in a 40-21 loss to BYU last season.
Said Brown at the time: "You can look at it as panic. I'm trying to fix it."
Louisiana Tech (4-8) ranked 63rd nationally in total defense last season, giving up an average of 408.2 yards and 26.3 points per game.
ESPN's Joe Schad and The Associated Press contributed to this report.