Del Rio interviewed with USC Athletic Director Pat Haden after Lane Kiffin was fired during the 2013 season.
Haden eventually hired Steve Sarkisian, who led USC to a 9-4 record in his first season.
"It's a great place," Del Rio said of USC last January, a few days before the Broncos played the Seattle Seahawks in the Super Bowl. “It just didn't work out timing-wise.”
Del Rio played linebacker at USC and was a consensus All-American in 1984.