The Matildas have been dealt another nightmare blow ahead of their next World Cup match, after emerging star Mary Fowler was ruled out.

Fowler suffered mild concussion on Tuesday and has subsequently been scratched from Thursday night’s game against Nigeria in Brisbane.

Fowler and defender Aivi Luik suffered mild concussions in separate incidents at Tuesday’s closed training. They were subsequently rulewd out of Thursday night’s game at Suncorp Stadium.

The loss of emerging star Fowler is another major setback for the Matildas after captain Sam Kerr was forced to sit out while nursing a calf injury.

The Australians are now without three forwards: Kerr (calf), Kyah Simon (knee) and Fowler.

Caitlin Foord is the only recognised striker available against the African side.

The 20-year-old Fowler had replaced Kerr as Foord’s starting strike partner in last week’s 1-0 win over Ireland.

Fowler’s concussion and Kerr’s injury will only increase scrutiny on the gamble to carry Simon through the tournament’s early stages, instead of picking a fully fit player, with a view to using her off the bench as an impact substitute later.

Simon was the shock inclusion in the squad announced on July 3, having not played a game since rupturing her left anterior cruciate ligament in October.

When asked if he regretted Simon’s selection, coach Tony Gustavsson told Optus Sport “definitely not”.

Football Australia said Fowler and Luik, who wasn’t used against the Irish, were fully recovered and in return-to-play protocols.

“We played an intense tempo game in training and unfortunately we had a couple of head knocks,” Gustavsson said.

“It’s up to the medical team to decide whether players are available or not.”

Football Australia’s concussion protocol rules players out for at least six days after a head knock. That opens the door for Fowler and Luik to play in the final group game against Canada in Melbourne on July 31, provided they clear the return-to-play program.

Fowler was walking laps at training on Wednesday and started running later in the 15-minute window available to media.

A week on from injuring her left calf, Kerr was walking laps on Wednesday, the most activity she has carried out in public since the injury was announced.

Kerr will be reassessed after the Nigeria game but given the tight, four-day turnaround to the Canada clash she appears unlikely to play.

The striker and her teammates have insisted Kerr will return to action during the tournament.

Simon was also walking laps at Brisbane’s Perry Park on Wednesday but Luik was not.

With Gustavsson unlikely to change the successful midfield pairing of Kyra Cooney-Cross and Katrina Gorry, experienced playmaker Emily van Egmond could line up alongside Foord.

Tameka Yallop, who has recovered from a corked thigh, and Alex Chidiac are other options to come in, while Cortnee Vine and Hayley Raso are the first-choice wingers.

Defender Alanna Kennedy was back in main training after missing Sunday and Monday for loading reasons.

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.

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

-with AAP