The Kookaburras, the world No.1 ranked team, had won an unprecedented four consecutive matches to begin the Tokyo Games

They looked on track for another thanks to a sharp Tom Wickham backstick tap-in from a penalty corner after 18 minutes.

But, after goalkeeper Andrew Charter had already repelled three late penalty corners, Pau Quemada's drag flick squeezed past his pad to secure Spain a quarter-final berth.

The Kookaburras, who have played five times in seven days, will still enter Sunday's quarter-final as their pool's top seed with their opponent to be decided after games later on Friday.

Australian coach Colin Batch said the scenario was an ideal dress rehearsal for Sunday's knockout fixture.

"They (Spain) were very motivated ... it was a different sort of game for sure," he said.

"It's easy to be disappointed and straight after the game the guys were.

"But the reality is we've played strongly and finished on top and qualified easily."

Australia held 59 per cent of possession and controlled play, but Spain arguably deserved their goal after earlier hitting the crossbar from a deflected shot and having another one disallowed on review.

Australia, an equal-worst sixth at the 2016 Olympics, are chasing their second men's hockey gold after a breakthrough 2004 triumph.

The Kookaburras are sweating on the fitness of Tom Craig, who suffered a leg injury in the tournament opener but could return for the knockout stage.

Belgium are the clear standouts in the opposing pool, winning all four games so far with a 24-7 combined scoreline.

Australian Associated Press