There was talk before these Olympics that it was time for the United States men's basketball programme to stop picking the creme of the NBA crop. Even they were getting bored by their dominance, it seemed.

But that chat has suddenly stopped on the back of an unconvincing final three games in pool play by coach Mike Krzyzewski's Team USA at the Rio Games. The unbackable gold medal favourites head into Wednesday's quarterfinals with a perfect 5-0 record, though with more of a stagger than a swagger.

The Americans, featuring NBA superstars Kevin Durant, Kyrie Irving, Klay Thompson and Carmelo Anthony, had opened pool play with huge victories over China (119-62) and Venezuela (113-69), neither of which did much to disprove the theory that it was time for the USA to, say, pick under-23 players so as to give their rivals a sniff.

POOL Demarcus Cousins (USA) and Rudy Gobert (FRA) of France struggle for a rebound. France out rebounded their much-vaunted opponents.

But then the worm has turned in Rio, starting with a feisty effort by Andrej Lemanis' Australian Boomers that might just have awakened the rest of the Rio men's hoops field that these Americans are not the unstoppable force of nature they would have you believe.

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The Boomers led the Americans by five at halftime, and hung tough throughout before succumbing to a 98-88 defeat. Afterwards there were even complaints from the US camp that the Australians had been a bit "dirty" with some overly physical play.

But the Australians did more than just nudge a few bodies out of the way.

They showed that the Americans can be unsettled if you stand up to them physically, and they also demonstrated that their interior defence is a little soft. The Boomers found that with some patience and ball movement that scoring on these NBA superstars wasn't so hard after all.

And so it has continued.

Serbia were next up and the European heavyweights shook off a bad start to go toe-to-toe with the Americans who needed a little luck to survive, 94-91. Only a missed Bogdan Bogdanovic three-pointer at the buzzer prevented the contest going into overtime.

The Serbians further underlined that Durant, Irving and co may just have a soft underbelly. They had trailed by 18 early, but worked their way back into the contest as their precision pass and cut offence found the US defence wanting.

A comment afterwards from US swingman Paul George was telling.

"Once again, we relied on natural talent," he told reporters in Rio. "This is why these guys are special in our league. These international guys really know how to move and really know how to cut. It's more about how they're running their offence. It's wearing us down.

"It's like they don't get tired."

And the trend continued as the US closed out pool play on Monday against a France side that elected to rest star guard Tony Parker to allow a toe injury to heal ahead of the knockout rounds.

Still, the undermanned French came out and played the Americans to the limit before going down 100-97. Like the Serbians, Les Bleus were able to score all too easily against the suspect US defence, shooting 56 percent from the floor and also nudging the rebound count 35-29.

The US have now won 50 straight games in Fiba international play, and there is every chance they will extend that to 53 over the closing stages of this tournament as they secure another gold medal.

But the last few days have reinforced the fact that for all their talent, all their wealth (Team USA's collective annual salary in Rio is well north of $US200 million) and all their firepower, they remain vulnerable to a well-coached, well-drilled team that plays hard and looks after the ball.

And for now that talk of handicapping themselves back to the field has gone as quiet as the American fans at the Rio arena.

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