Emerging star Mary Fowler has been ruled out of the Matildas' Women's World Cup clash against Nigeria with concussion.

Fowler and veteran defender Aivi Luik suffered mild concussions in separate incidents at Tuesday's training and were subsequently scratched from Thursday night's game at Lang Park.

It is a huge blow for the Matildas, who are now without three forwards: Captain Sam Kerr (calf), Kyah Simon (knee) and Fowler, with Caitlin Foord the only recognised striker available against the African side.

Fowler had been poised to line up alongside Foord for a second consecutive match in Kerr's absence.

The 20-year-old made her World Cup debut in the opening 1-0 win over Ireland.

Football Australia said Fowler and Luik were fully recovered but were unable to play under concussion protocols.

As the only team in Group B with three points from their opening game, Australia can seal progression to the knockout stages with victory over Nigeria, who have one point so far.

If Canada (one point) and Ireland (zero points) draw in Perth on Wednesday night, a win on Thursday would lock in top spot for the Matildas ahead of their third group game.

AAP