In the winning-is-everything culture of big-time college basketball, coaches typically leave their posts for one of two reasons: They’re fired for their teams’ poor performance or they quit before their contracts are up, bailing for bigger paychecks and more prestige elsewhere.

Maryland’s Gary Williams followed neither script Thursday, choosing an unremarkable afternoon to announce that he was retiring after 22 seasons, “fiercely proud” of the program he had helped build at College Park, leading his alma mater to a national championship, two NCAA Final Fours and a 461-252 record.

It came as a shock to Terrapins fans and even to many close to him, including the team’s graduating seniors, who posed with their coach earlier in the day without any idea his retirement was at hand.

Washington area sports fans barely had time to digest the fact that the Capitals had been swept from yet another National Hockey League playoff series when sports talk radio was interrupted by news that Williams, the region’s longest-tenured coach of any sport, was stepping down. Williams noted simply, in a statement released by the university, “It’s the right time.”

In an interview, Williams, 66, explained that he started thinking about retiring in March 2010, after Maryland upset Duke at Comcast Center to clinch a share of the ACC’s regular season championship. But after the departure of then-Maryland athletic director Debbie Yow, with whom he’d had a strained relationship, Williams decided to stay another year and see if his zeal for the job didn’t return.

Though he said he enjoyed working with the Terps’ new athletic director, Kevin Anderson, Williams said: “I think I’d been worn down by the previous 15 years. It grinds on you.”

Williams is expected to elaborate on his decision Friday, when he’ll meet with reporters at a news conference that’s being staged at 17,950-seat Comcast Center, with Terrapin alumni, fans and supporters invited to attend.

Within minutes of Williams’s resignation, speculation began about his successor. His departure comes less than six months after Maryland ousted its football coach, Ralph Friedgen, who was also a Maryland graduate. But it’s doubtful the Terps’ next basketball coach will be a product of the university.

Villanova Coach Jay Wright is high on Maryland’s list to replace Williams, according to an individual familiar with the situation. Wright is a widely respected former Big East coach of the year with ties to the area. Notre Dame Coach Mike Brey, a Bethesda native who attended DeMatha, is reportedly interested. Maryland officials contacted Brey, this past season’s Big East coach of the year, on Thursday, according to the Chicago Tribune, but he may be working on a contract extension at Notre Dame.

A source also cited Arizona Coach Sean Miller as a potential candidate.

Williams, for his part, doesn’t plan to stray far from College Park. He’ll stay on with the university as an assistant athletic director and special assistant to Anderson, working closely with the Terrapin Club to raise money for scholarships and the athletic department in general.

Williams made something of a sacrifice 22 years ago in leaving his job as head coach at Ohio State to help rehabilitate the men’s basketball program at Maryland, which was still reeling from the death of its star player Len Bias and facing NCAA violations incurred during the three-year tenure of Bob Wade.

Leaving Ohio State for Maryland at the time was deemed a lateral move, at best. But the tug of his alma mater proved strong for the scrappy former guard who never thought he’d amount to much more than a high-school basketball coach.

Williams got his big break at American University, taking over as coach in 1978. After four years, he took the reins at Boston College and then, Ohio State.

Maryland was slapped with a two-year ban from the NCAA tournament in March 1990, less than one year into Williams’s tenure, because of previous transgressions. His teams slogged through two losing seasons. Then, beginning in 1994, came 11 consecutive NCAA tournament appearances. In 2001, Maryland finished 25-11 and advanced to its first Final Four, losing to Duke. The next year, Williams led Maryland to its first national title with a largely unheralded bunch of players who shared their coach’s competitive fire, defeating Indiana, 64-52.

“He built such an amazing thing at Maryland, and it was largely on the force of personality,” said Chris Knoche, a former player, assistant coach and now color commentator for the Terrapins’ radio broadcast. “He certainly had some very, very good players who helped them become what they became. But you’d be hard pressed to dispute the fact that Gary Williams was the biggest star of all of them.”

That said, the Terps’ fortunes were spotty in recent years. Maryland failed to earn a coveted berth in the NCAA tournament four of the last seven years. This past season was a particular disappointment, with Maryland finishing 19-14 (7-9 in the ACC) and failing to be invited to either the NCAA or lesser-tier National Invitation Tournament for the first time since 1993.

On Wednesday, Maryland’s leading scorer and rebounder, sophomore Jordan Williams, acknowledged that he had signed with a sports agent in preparation for June’s NBA draft — effectively ending his college career.

When he shared the news with his players Thursday afternoon, Williams told them he hoped they felt he had given them everything he had. He acknowledged the decision was difficult, but part of life. And he assured them they’d all be fine and thrive under whoever succeeded him.

“Players are more resilient than old people are,” Williams said.

“How many people do the same thing for 43 years? I’m sad I won’t be a part of it any more the way I have been and won’t have the relationships I’ve had with the players. But I’m looking forward to not always worrying about the next game, the next recruit, the next season. I can’t remember the last time in my life there wasn’t a ‘next thing’ I had to be concerned about.”

Staff writer John Feinstein contributed to this report.