Jack Del Rio will fill in for John Fox. (Charles Rex Arbogast / AP)

The first of two NFL coaches who experienced health problems over the weekend has undergone surgery and begins an unspecified period of recovery as the focus falls on the physical toll that coaching takes.

Denver Broncos Coach John Fox underwent aortic-valve surgery this morning in a Charlotte, N.C., hospital and defensive coordinator Jack Del Rio stepped into Fox’s job on an interim basis. Fox was aware of his heart problem and had hoped to put off corrective surgery until after the season, but his hand was forced when he experienced light-headedness Saturday on a golf course. “This is a serious thing for John,” John Elway, the Broncos’ vice-president of football operations, told reporters. “This was a serious procedure. Fortunately, from what we’ve heard, things went well.”

In Houston, Texans Coach Gary Kubiak remained hospitalized and is undergoing tests after he collapsed during the Sunday night game against the Indianapolis Colts.

Elway is acutely aware of just how taxing it is to coach at a high level. His father, Jack, was a lifelong coach and “the last person on the totem pole [coaches] they take care of is themselves.”

In New York, Giants Coach Tom Coughlin admitted that stress was part of the job. “When you sign up for it, it kind of goes along with it — unless somehow the competitive aspect of the game changes,” he said (via Ralph Vacchiano of the New York Daily News). “It’s just as much that as it is anything else. It’s all about grinding away inside, the competitive part of this thing. It’s part of it. It’s what the individuals are made of at this level.” Joe Gibbs, the former Washington Redskins coach, has Type II diabetes and had a stent placed in an artery during his second go-round in Washington. “You wind up having to coach yourself,” Gibbs told the News-Observer last spring. “I’ve learned so many things by making a mistake. Then you go back, you start studying and you ask questions.”

Fox is the second NFL coach in two years to take an extended leave midseason because of a health crisis. Last season, Chuck Pagano of the Indianapolis Colts had to leave the team to undergo treatment for leukemia. Elway said he’d reached out to Colts General Manager Ryan Grigson for advice on how to handle the situation. Del Rio indicated that he hoped to speak with Arizona Cardinals Coach Bruce Arians, who filled in for Pagano last season and led the Colts into the playoffs.

But, as with Pagano, there’s a bigger issue for Fox and Kubiak.

“The docs are going to tell us the right thing to do,” Elway said. “The concern is with John’s health, not just this season but the rest of his life.”