Mike Stoops has been fired as Oklahoma's defensive coordinator on the heels of the Sooners' 48-45 loss on Saturday to Texas.

The school announced the firing Monday. Ruffin McNeill, who had been the Sooners' assistant head coach and defensive-tackles coach, will serve as defensive coordinator for the rest of the season.

"At the end of the day, I felt like we needed a new voice," coach Lincoln Riley said Monday. "We needed just a little bit of a spark. I thought that making the change was right for that reason, and also because I felt good about the guys we have in this room and a plan for the rest of this season. This team's got a lot in front of them. This team could make a run here. I think we all feel that."

Stoops, the younger brother of former Oklahoma coach Bob Stoops and older brother of Kentucky coach Mark Stoops, had served two different stints as the Sooners' defensive coordinator. He returned to Oklahoma in 2012 after an eight-year run as Arizona head coach.

Mike Stoops was also at Oklahoma from 1999 to 2003, as assistant head coach and co-defensive coordinator.

The 48 points by Texas on Saturday were the most ever scored against Oklahoma in the Red River Showdown. The Sooners hadn't given up more than 27 points in their first four games this season, but allowed 33 in the victory over Baylor two weeks ago and then 48 -- and 501 total yards -- in their first loss of the season to the Longhorns.

Riley said the decision was his alone, and he didn't make it based on just the Texas game.

"I don't know that there was any one stat or one thing or any single thing that happened," Riley said. "It's not really that dramatic. I think just for me it was a gut feeling. Coming back after that [Texas] game and just thinking through it, I slept on it, and [after] conversations with Mike and other people I respect, I just felt like it was the right thing to do."

Riley's confidence in McNeill played a role in the decision to fire Stoops. Riley was McNeill's offensive coordinator at East Carolina, and he brought McNeill to Oklahoma as assistant head coach before the 2017 season.

McNeill was defensive coordinator at UNLV from 1997 to 1998 and at Fresno State in 1999. He later served in that same role with Texas Tech from 2008 to 2009 before taking over as head coach at East Carolina from 2010 to 2015.

"I have a ton of confidence in Ruffin," Riley said. "There's not really anything in this game that he hasn't done. He's one of those guys that, when something like this comes at us, he doesn't have to sit back and figure out how he's going to handle it. He knows how he's going to handle it the second the situation's presented."

Oklahoma players reacted to the news on Twitter.

"All I can say is thank you @OU-CoachMike you gave me a shot when nobody else would and for that I am forever grateful no matter what people say they never know you for the great person you really are and how much you care for your players...Thank You Coach," linebacker Kenneth Murray tweeted.

The No. 11 Sooners (5-1, 2-1 Big 12) have a week off before they play at TCU, which will give them time to adjust. Riley said the players are comfortable with McNeill, which should help in the transition.

"He does have a confidence about himself," Riley said. "He's got a way with the players. They'll be excited to play for him."

Bob Diaco will move from defensive specialist to coach the outside linebackers. He has been defensive coordinator at Cincinnati, Notre Dame and Nebraska and was head coach at Connecticut from 2014 to 2016.

Information from The Associated Press was used in this report.