Tony Gustavsson has found himself a surprise ally in three-time NRL premiership-winning coach Trent Robinson after the Matildas boss kept news of Sam Kerr's calf injury bombshell under wraps.

Kerr was ruled out of Australia's opening World Cup win over Ireland 90 minutes before kick-off and is no certainty to play before the knockout stages.

Gustavsson, his players and staff had managed to keep Kerr's fitness in house despite the fact she pulled up sore during their final run before the 1-0 win over Ireland.

The Swede even fronted a press conference with Kerr and gave little hint the Matildas would be without their iconic forward.

Robinson had to endure a similar scenario in the Sydney Roosters' 2018 premiership success when halfback Cooper Cronk was under an injury cloud and looked unlikely to feature.

It wasn't known until an hour before kick-off Cronk would play through the pain barrier of a serious shoulder injury on the way to a grand final victory.

Gustavsson made no apology for failing to disclose the issue earlier and Robinson praised the Matildas manager's ability to maintain a straight face.

"The objective of a coach is to win the game, other people might have different opinions," Robinson said.

The Roosters mentor said declaring Kerr's unavailability would have only handed Ireland the chance to change their approach.

"Our job is to create intrigue and guessing in the opposition and showing your cards in the days and weeks before a game, that's giving a tip sheet to the opposition," Robinson said.

"People wouldn't have turned up if they found out? People wouldn't have watched?

"The coach's job for Australia is to win the game, and if that was a tactical advantage so Australia could win the game then I think we're happy with that as Australians rather than having the knowledge hours before that Sam wasn't playing."