Olympic sea king MICHAEL PHELPS is passionate about poker – and pals fear it could destroy his future!

The 27-year-old sports phenom – the most decorated Olympian ever with 22 medals – hangs out with pro poker players and has already gambled away a small fortune, in­siders say.

Now that his swimming career is over, pals worry Phelps will channel his competitive streak into poker and squander the endorsement jackpot that he’s struggled for years to achieve.

“All Michael thinks about is gam­bling,” said a poker-playing crony of the Baltimore-based superstar.

When he’s home in Maryland, Michael plays in a weekly card game where the buy-in is $25,000. Michael has wagered hundreds of thousands of dollars on poker already, and now that he’s retired from competitive swimming, every­one’s worried he’ll be betting mil­lions more.”

Before the closing ceremonies for the London games, Phelps raised eyebrows by jetting off to the Mal­dives, a group of islands in the In­dian Ocean, with his poker-playing posse. Even his former roommate, Jeff Gross is a poker pro.

“Michael would love nothing more than to embark on a career as a professional poker player,” said the source.

“But unlike Mike, his professional poker-playing buddies know when to fold ’em and walk away. Michael has a ‘don’t quit until you win’ atti­tude which was great while he was

swimming but could be costly playing poker.”

According to pro poker play­er Phil Collins, a close pal of Phelps, the Olympic hero “talks about poker all the time. We have to tell him every once in a while, ‘Jeez, Mike. We play for a living. Can we take a break?’”

Phelps admitted: “I love to play poker. I’ve been playing for a few years…I’ve met some of my best friends at a poker table.”

He also says he used on­line poker to help him learn the game, starting with $1 to $2 games and graduating to $100 to $200 no limit games.

A poker insider told The ENQUIRER : “In online bet­ting for high stakes, there usu­ally is a standard $20,000 buy-in, and a player can easily lose six figures in an afternoon.”

Even the in­famous photo of Phelps smok­ing pot at a party in Columbia, S.C., after the 2008 Olympics has a poker connection.

The “bong” Phelps was using belonged to poker champion Zachary “Carter” King, 26, who was later arrested for pot possession in an unrelated incident.

“This is not a good element for Michael to be hanging out with,” said a source. “It’s just going to get him in trouble – big trouble!”

Now his protective mom Debbie fears that her son might self-de­struct without the discipline of daily training and the guidance of his longtime swimming coach, Bob Bowman.

For now, Phelps is worth an esti­mated $45 million, but experts say future endorsements could triple that – if he keeps his nose clean.

“Michael is on top of the world right now,” said an insider. “But if he lets the gambling, the girls and the high living get the best of him, it could all come crashing down!”