When Bob Stoops looked around the coaching landscape watching his peers work themselves to exhaustion, he always came to the same conclusion.

"When I'm 65," he once told me, "I'm going to be on a beach somewhere."

Stoops got one heck of a shocking head start on the surf and sand Wednesday, announcing his retirement at Oklahoma.

Shocking because Stoops, 56, was still in the heart of his career and has his health.

Shocking because it's the first week of June.

Shocking because the Sooners are expected to be hovering near the top five to start the season.

But the nation's longest-tenured coach at one school (18 years) nevertheless called it quits Wednesday. No coach during that span has won more games (190). "Big Game Bob" will go down as arguably the greatest coach in Big 12 history.

A product of hardscrabble Youngstown, Ohio, Stoops never lost that edge bred in him by his hometown. But he loved to enjoy life. Those who knew him best were familiar as much with his high-pitched laugh as they were his 10 conference titles and 2000 national championship.

"Bob never said anything about retiring in my recent conversations with him," said former OU assistant Mark Mangino, who spoke with Stoops two weeks ago. "But Bob used to say all the time, 'I'm not going to do this forever.'"

And so he won't. Stoops will remain at Oklahoma as a special assistant to athletic director Joe Castiglione after compiling a 190-48 record (101-9 at home). No FBS coach coach has won as many games since 1999. There are now only 16 FBS coaches who have won Power Five conference titles.   

Stoops' perspective showed through in comments to CBS Sports less than a year ago. Asked about retirement, Stoops said: "As things change, you never know what can come."

Still, the arrow was pointing up at Oklahoma. Stoops had a returning Heisman Trophy finalist quarterback in Baker Mayfield. The Sooners had just knocked off Auburn in the Sugar Bowl. Oklahoma is less than two years away from a College Football Playoff appearance.

For an intensely competitive man, this promised to be one of the best years in the state of Oklahoma with Oklahoma State flashing top 10 potential as well.

There was immediate speculation regarding health concerns. Stoops father, Ron Sr., died at age 54 on the way to the hospital after having a heart attack while coaching Cardinal Mooney High School in Youngstown.

"The timing is very strange," an Oklahoma source said of Stoops. "I know over the years he's been concerned about a genetic heart situation in his family."

Sources said Stoops may have been concerned about his own cholesterol issues.

"I understand there has been some speculation about my health," he said in a statement released by the school. "My health was not the deciding factor in this decision, and I've had no incidents that would keep me from coaching."

The decision may be as simple as Stoops seeing his sons grow up. Drake and Isaac Stoops are rising seniors at Norman North High School. Both are expected to be Division I recruits.

They will not have the chance to play for their dad. Offensive coordinator Lincoln Riley takes over. The 33-year-old Riley immediately becomes the youngest head coach in the FBS.

That is less of a surprise. It was no secret that Riley -- a protégé of Mike Leach while at Texas Tech -- was being groomed for the job. The Oklahoma board of trustees recently upped his salary to $1.3 million while extending his contract three years as offensive coordinator. That sum will obviously will increase.

Riley's relative inexperience shouldn't be a surprise. Stoops took the Oklahoma job when he was 39 after leaving Steve Spurrier's side as Florida's defensive coordinator in 1998.

Legendary coach Bud Wilkinson was 31 when he took over the Sooners in 1947. Oklahoma's winningest coach, Barry Switzer, was 34 when he took the job.

The news caught Nick Saban by surprise like most of us. The iconic coach was in a staff meeting room Wednesday at Alabama when he heard of Stoops retirement.

"Bob is a great friend and one of the best coaches in the country during his time at Oklahoma," Saban said. "I have had the pleasure of knowing him and his family for over 40 years. I have always had so much respect for Bob because of his professionalism and integrity."

With the season less than three months away, it certainly was an odd time to step away. The Sooners are in the middle of offseason conditioning. There was no known crisis that would force him out.

His wife, Carol, was once a highly successful Mary Kay rep. The family just bought a second property in Chicago, Carol's favorite city. Stoops also has a home near Jacksonville, Florida.

"He wants to enjoy life and just be one of the guys," Mangino said.

At the end of the month, Mangino, Stoops and other Youngstown-area coaching natives will reunite in the town for the annual bocce ball tournament the benefits Cardinal Mooney.

Stoops' name, especially earlier in his career, seemed to be constantly linked to major job openings most notably at Florida and Notre Dame. But Stoops always felt the security of Oklahoma. With president David Boren and Castiglione, they were the only three men who'd been in their positions together at the same school since 1998.

Stoops walks away having coached two Heisman Trophy winners (Jason White, Sam Bradford). He'll never get to chase that elusive second national championship.

The beach isn't a bad alternative.

"No question he's going to go down as one of the greatest football coaches the game has had," Mangino said. "The run he's had at Oklahoma has been unbelievable."