Lincoln Riley Says Leaving Oklahoma For USC Was Tough, 'Very Sudden'

Lincoln Riley is opening up on his shocking exit from Oklahoma ... saying leaving the Sooners was a "tough" and "emotional" decision, and admitting he initially thought he'd decline USC's offer.

Riley joined Colin Cowherd on 'The Herd' Tuesday morning ... and Southern Cal's newest coach revealed just how quick the process actually was.

"It was very sudden. I was totally committed to our team as we made a championship and playoff run," Riley said. "And I made that clear to anybody that was interested."

Lincoln says that USC showed serious interest in bringing him on board ... and that by the time he met with them in person, he could sense the Trojans were the perfect fit for him.

"You could feel their energy," he added. "You could feel their leadership from the very top is willing to do the things that maybe haven't been done here as of recent to get USC to where it needs to be," Riley said.

The 38-year-old said he was initially reluctant to accept USC's offer saying ... "I honestly didn't think I would do it. I really didn't."

Lincoln also reflected on how leaving Oklahoma -- historically a football powerhouse -- meant way more than simply leaving an elite football program ... adding that the seven years he spent there featured some of the best moments of his life, including the birth of his second daughter.

Riley enjoyed success at Oklahoma -- the university went to four Bowl games under his watch -- and he's optimistic about his fresh start with his new team.

"When you combine that commitment from the people in this university with the history, the tradition, the opportunities here at USC, the future is so bright."