Did burnout force Riley's hand?

At no time on the NBA calendar does a coach get more time on the practice floor than October.

So . . .

Knowing that -- and knowing how much Pat Riley reveres the sanctity of the practice floor -- leaves us with only a couple of plausible explanations for the announcement Friday that blindsided the NBA.

What kind of coach is Stan Van Gundy?

Like brother Jeff, Stan is a devoted Riley disciple who treasures defense and toughness and hours upon hours of painstaking preparation. The hope of Heat management is that the transition the players now face will progress more quickly than it might have simply because Stan Van Gundy's approach is so Riles-like.

Another potential boost for the stunned Heat: Van Gundy, according to team sources, often took the in-charge role from Riley during training camp this month in what now appears to be a foreshadowing of Friday's coaching change.

"Stan will do well," said longtime Heat guard Tim Hardaway. "The only thing I'm scared about is that Stan takes this very, very, very, very, very seriously. He's like his brother. I hope he doesn't burn out like his brother did [in New York]. They take it so seriously, they don't go home."

-- Marc Stein

Only one of two things could motivate Riley to announce his resignation from coaching five days before the season starts, after eating up almost all of that October practice time replacement Stan Van Gundy now could surely use.

Either Riley came to training camp hoping that the mental fatigue inflicted by the first two losing seasons of his career would start to fade once he threw himself back into work, only to discover that he didn't have enough resolve left to get through even one more season ...

... or Riley feared that the league's lesser-known Van Gundy would not be given the opportunity to replace him, as Riley has long wanted, unless he resigned in a manner that left no time to search for replacements.

It has to be one or the other. There is no other sensible explanation, barring a health problem no one knows about, to rationalize the sight of Riley stepping up to a podium without any real warning and suddenly retreating to the front office, thus leaving his successor with almost no time to properly prepare the Heat for their first game Tuesday night in Philadelphia.

Although he has been hinting that the end was near for more than two years, Riley had convinced no one that he was seriously thinking about leaving. That includes Van Gundy, who figured Riley would change his mind after they discussed the transfer of power Wednesday.

"I just believe, deep down in my heart, that I think you have to listen to your heart and listen to your instincts," Riley said at his farewell news conference.

"And I've done it."

Riley did it even though the Heat, after a string of playoff disappointments and two excruciatingly poor seasons, rebounded with a pretty good summer. Riles favorite Alonzo Mourning took his fight against kidney disease to New Jersey, but the Heat drafted promising guard Dwyane Wade with the No. 5 overall pick. After missing out on Elton Brand, Riles then constructed a contract offer rich enough to secure one of his favorite players, as the Los Angeles Clippers declined to match Miami's $64 million offer sheet to free-agent forward Lamar Odom.

In a bid to convince the Clippers to let him go, Odom announced that he didn't see himself playing for any other coach besides Riley. He told ESPN.com that playing for the Heat was his destiny, saying in August: "Me and Coach Riley, we have a great relationship for two guys who haven't come together like we were supposed to."

Yet apparently not even Odom's arrival could sufficiently re-energize Riley, who insists that no other factors -- not failing health, nor the theory about helping Van Gundy get his head-coaching shot -- led to his stunning exit.

"Nobody saw this coming," said former Heat guard Tim Hardaway, Riley's floor general in the Heat's best years. "Nobody, nobody, nobody.

"I thought he was going to be there for the next two years. But I think the last couple of years have taken a big toll on him. A big toll. He's gone for 21 years nonstop. I guess he's just tired. He could be burned out. He says it's not a health situation, and I hope it's not. He's had a great career, a great run, but maybe he just needs to sit down for a couple of years and get rejuvenated."

Much of the immediate reaction around the league Friday endorsed that line of thinking, suggesting that Riley's return to an NBA bench is inevitable. At 58, Riley has two seasons left on his original 10-year commitment to Heat owner Micky Arison, and it's difficult to imagine the self-anointed Winner Within -- who went 19 straight seasons without missing the playoffs -- walking away for good after finishes of 36-46 and 25-57.

Fact is, though, Riley can spruce up the only badly smudged section of his legacy by being the devoted and successful front-office man he vowed to be Friday. It has been said often, since the Heat's spiral commenced, that Riles The Executive was the worst thing that ever happened to Riles The Coach.

Bad fortune certainly played a part in recent seasons, with Mourning stricken by kidney failure and Hardaway's knees ravaged by injury. But it was Riley's decision alone to build around Eddie Jones and Brian Grant. Neither member of that $170-plus million combination has approached franchise-player status.

Nothing detracts from the rest of Riley's resume. Four championships with the Lakers. Back-to-back titles in 1987 and 1988 . . . after he famously guaranteed the second one. He also came within one game of leading New York to a championship in 1994, after resuscitating the long-dormant Knicks, and quickly established the Heat as New York's chief rival.

Yet it remains to be seen what kind of impact he can have solely as an executive, or if he can stand being that far removed any more than he could stand the Heat's ongoing on-court struggles.

"Lamar is someone I need to talk to (more) about this," Riley admitted. "But I'm going to be with him, on him, in him, working with him. I'm not going to be someone who sits behind a desk."

He better not. He better find a way to nurture Wade and Odom from afar, hard as that sounds, because they both need guidance much more than they need a rookie coach.

Riley better give us something else -- something good -- to talk about, unless he's prepared to endure questions about his bizarre timing for a while.

Marc Stein is the senior NBA writer for ESPN.com. To e-mail him, click here. Also, send Stein a question for possible use on ESPNEWS.