The Opals have not minced their words after an upset loss to Nigeria put their 2024 Olympic medal hopes in early jeopardy.

Nigeria ran out winners 75-62 at Lille Stadium on Monday night.

Opal Steph Talbot said post-match while they knew in advance the African side would deploy a full-court press, they still didn't handle it well.

"It's not good enough, it's not Opals basketball. We need to learn from it and move on, and we need to get the next two wins," she said.

Coach Sandy Brondello was equally frank about what went wrong.

"Everything, really," she said. 

"We came out with the turnovers, we couldn't handle any kind of pressure. We weren't real quick learners, we kept doing the same thing over and over.

"We didn't play Opals basketball, defensively too. We weren't aggressive. We got aggressive in the second half and in that third quarter in particular and that helped us, but we ran out of legs a little bit. But we have to be better."

Starting the game well, the Aussies soon found themselves with an unshakable problem of turning the ball over, and Nigeria made them pay.

Led by Ezinne Kalu with 17 points in the first half, they fired away from long range and rushed Australia's shaky offence to earn their greatest Olympic basketball win.

Alanna Smith top scored with 15 points for the Opals, but missed two late sets of free throws. The Opals only converted eight of a possible 18 points from the line, which thwarted their chances to return to the lead.

It is a major dent in Lauren Jackson's (six points, two rebounds in 12 minutes) plans for a fifth medal in as many Games — the 43-year-old back on the Olympic stage for the first time since London' 2012.

They will play world number five Canada on Thursday and seventh-ranked France on Sunday, with only the pool's top two sides guaranteed a berth in Paris's quarterfinal stage.

The Opals, without a medal in their last two Olympic campaigns, began with confidence, running plays at will and leading 8-2 before the wheels fell off.

Turnovers were contagious, with Marianna Tolo the only Opal with court time not to commit one while six of her teammates had two each.

Sandy Brondello's side ultimately turned the ball over 26 times.

Half time couldn't come soon enough, Nigeria's high press causing significant headaches as the Opals continually coughed the ball up while walking it up court.

An 11-0 run led by Kalu gave Nigeria a 41-28 lead at the main break.

Triples to Sami Whitcomb and Alanna Smith helped as the Opals found some rhythm and quickly got within five points with a 12-4 start to the third term.

It was a two-point game early in the final term and an Opals' lead seemed inevitable.

But again the Australians were their own worst enemies, a Jackson fumble under the hoop creating a five-point swing when Nigeria's Elizabeth Balogun hit a deep three at the other end.

Missed free throws were just as tough to swallow, Australians at one stage making just one of six to cost themselves another lead.

Nigerian captain Amy Okonkwo did not need another invitation, burying a three-pointer to put her side ahead by seven entering the final four minutes and sparked tears of joy after full-time.

AAP