The AFL has admitted to an embarrassing interchange error in Sydney’s 13-point win over Fremantle, which gifted the Dockers a goal in the third quarter.

A Swans official incorrectly filled out the paperwork required when Ryan O’Keefe was substituted from the ground.

It should have resulted in a financial sanction, but instead a free kick was paid – as is the case with major interchange infringements.

A short story on the AFL’s website confirmed it was the “wrong call”.

The club, including coach John Longmire, was understood to be ropable with the incorrect ruling – which came in the middle of the Dockers’ six-goal blitz in the third term.

It’s the second consecutive year Sydney have been on the wrong side of a controversial interchange infringement.

The AFL last year apologised to the Swans for incorrectly paying a 50m penalty and free kick to Carlton during a crucial stage of the round-six clash at the SCG.

An interchange steward had incorrectly believed Dan Hannebery entered the field as Sydney’s 19th man.