ENGLEWOOD, Colo. (AP) — One of John Fox’s favorite sayings is “Next man up.”

Whenever a starter goes out, his replacement needs to step right in and keep things rolling.

This time, that next man up is defensive coordinator Jack Del Rio, who’s in charge of the Denver Broncos while their head coach recovers from heart surgery.

While Del Rio was running his first practice as the Broncos interim coach Monday, Fox was in the recovery room at Carolinas HeathCare System’s Sanger Heart & Vascular Institute in Charlotte, N.C., after having his aortic valve replaced in an operation he had hoped to delay until after the Super Bowl.

“We all wish him a speedy recovery. The best way that we could honor him is to go out and play great football,” Del Rio said after taking over a 7-1 team that’s the prohibitive Super Bowl favorite even though the Broncos trail the unbeaten Kansas City Chiefs (9-0) in their own division.

Fox’s wife, Robin, issued a statement through the team that said Fox’s operation went well and he was being monitored in the hospital’s post-operative critical care unit.

“Along with his medical team, we will take great care of him so he can fully recover and get back to coaching the Broncos as soon as possible,” she said.

Del Rio, who spent nearly nine seasons as Jacksonville’s head coach before joining Fox’s staff last year, said he’s honored to serve as caretaker of Fox’s team.

“We’re on a mission to carry on and continue the things that Coach Fox has instilled and started with this football team,” Del Rio said. “This is Coach Fox’s team. I’m merely the person that’s able to keep it running right now while he’s healing.”