Robinson served as Texas's defensive coordinator in 2004, when Texas went 11-1 and won the Rose Bowl, and had been working as a football analyst in the Texas player personnel department at the time of the position shift. Diaz will be reassigned to a position within the Texas athletics department.
"Our performance on defense last night was unacceptable, and we need to change that," said Texas coach Mack Brown. "Greg will be here tonight and get with the staff and players to start preparing for Ole Miss. He will be running our defense immediately. We're very fortunate that Greg has been around, watched all of our practice video and has a good scouting report moving forward. His familiarity with the staff and players should make for a smooth transition. He knows this place, did a terrific job in leading our defense before, and I'm excited to have him back on the field. We're back at it and working hard to beat Ole Miss this weekend."
Texas allowed a school-record 550 rushing yards on Saturday night in a 40-21 loss to BYU, and after the game, Brown said that he would have to watch the film to see if Diaz would be retained. His decision came less than 24 hours later.
Robinson has coached for 36 years and was the defensive coordinator on two Super Bowl winning teams. The 2004 Rose Bowl squad laid the foundation for a 2005 team that went on to win Brown's lone BCS National Championship.
"This is a tough deal for everyone involved, but I love The University of Texas, and Coach Brown has been wonderful to me," Robinson said. "I'll do anything I can to help him, so when he called, I told him I'd be there today. I know the staff, have a lot of respect for them and am excited for the challenge moving forward.
"I've been around the team a lot, watched all of their film and have been self scouting and scouting opponents since I came on board in July. Because of Longhorn Network, I've also been able to see these guys for two to three years and am very familiar with the personnel."
Robinson was most recently a defensive coordinator at Michigan for two years (2009-10), right after four years as head coach at Syracuse (2005-08). Robinson was Texas's co-defensive coordinator along with Duane Akina, and the team's linebackers coach, for the 2004 season. In that year, Texas held its opponents to 320.1 yards (23rd in NCAA) and 17.9 points per game (18th NCAA), while ranking 16th in rushing defense (107.4 YPG).
"I need to get with the staff, work with them to get a plan in place and hit the ground running," Robinson said. "I think very highly of the defensive coaches I'm working with — Duane (Akina), Oscar (Giles) and Bo (Davis) — so it's critical for me to get with them and figure out what specifically we need to do moving forward. Having coached here, I do know the ins and outs and having the stability with the rest of the staff will be very beneficial."
Before Texas, Robinson spent 14 years coaching in the NFL, starting as the New York Jets' defensive line coach for four seasons (1990-93) before moving to defensive coordinator (1994) and eventually on to defensive coordinator for the Denver Broncos (1995-2000) and Kansas City Chiefs (2001-03). Robinson was the Broncos' defensive coordinator when they won back-to-back Super Bowl titles in 1997 and 1998.
Prior to his time in the NFL, Robinson started at the University of the Pacific (1975-76), moving on to Cal State Fullerton (1977-79), N.C. State (1980-81) and then UCLA (1982-89). In his final season at UCLA, Robinson was the team's offensive coordinator.