Australia's captain Sam Kerr will be given until the last minute to prove her fitness for their must-win Women's World Cup clash against Canada on Monday, coach Tony Gustavsson says.

The prolific striker missed Australia's opening two games – a 1-0 win over Ireland and Thursday's shock 3-2 loss to Nigeria – with a calf injury.

With the co-hosts' hopes of reaching the last 16 now in jeopardy, Gustavsson is desperate to have the Chelsea forward available.

"We won't get confirmation (on her fitness) until the night before the game, and it might even be where we need to test her to see if she can play on game day," Gustavsson said.

"That's how tight it is."

Kerr watched from the sidelines in Brisbane as Australia took the lead against Nigeria, only for the Super Falcons to fight back and silence the home crowd.

"She's going to do anything she can to be out there," Gustavsson added.

"I know that she'll want to be out there and she deserves to be out there.

"If she's available we're going to need to come up with a plan together to see what we can do to maximise the potential minutes she has – if she's available."

Gustavsson insisted that he was upbeat about the Matildas' performance despite the shock loss to a clinical Nigeria.

"We had 28 shots, scored two goals, the attacking game was much, much improved compared to the Ireland game," he said, referring to the 1-0 win over the Irish, via a penalty, that opened their campaign.

"I'm disappointed about the result but I can't let the result blind the performance.

"I know it's hard to see, but there is part of this performance that is better than the result shows."

Gustavsson now needs to pick up his players.

"The physical recovery is one thing but the mental recovery is another," he said.

"But the one thing I know about this team – and you saw it in the last 10 minutes of this match – is the never-say-die attitude.

"They are brave and they play all the way through, and it almost got us a tie today.

"It's definitely one of the most important things we have to prepare for, to mentally bounce back."