Rebecca Allen has been left "shattered" after a hamstring injury in the Opals' final warm-up game robbed her of a second Olympic appearance in Paris.

The smooth-shooting guard, who plays for the Phoenix Mercury in the WNBA, will be a huge loss for Sandy Brondello's side when the campaign commences against Nigeria on Monday.

The 31-year-old aggravated a hamstring injury during the team's final practice match against Canada in Spain on Tuesday.

Scans undertaken in Paris determined the extent of the injury, with Allen deemed medically unfit to compete.

The setback comes after Allen unknowingly played in the Opals' charge to 2022 World Cup bronze with a partially collapsed lung and two broken ribs.

"I have been looking forward to these Games for a long time and am absolutely devastated but I will now focus my energies on recovery and supporting my Opals sisters," she said.

Travelling reserve Amy Atwell has been called in as her replacement.

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"Bec is such a big part of our team and has been for a long time, we are all devastated for her," Brondello said.

"This injury has come at a really unfortunate time and the call had to be made upon medical advice. Unfortunately she was not going to recover in time to play in these Games.

"Amy Atwell has been part of this Olympic squad all year and with us in Spain for our practice matches.

"This group has a really strong bond and connection and we will lock in, stay focused and continue our preparation for game one against Nigeria."

The Opals are looking to get back on the Olympic podium for the first time since taking home bronze at London 2012, adding to silvers from Sydney, Athens and Beijing, and a bronze at Atlanta in 1996.

They scraped out of the group stage in Tokyo before losing to nine-time gold medallists USA in the quarterfinals.

AAP