Collingwood has a battle on its hands to keep defender Tom Langdon.

The defender, one of the Pies best players in the grand final, has undergone a medical at Sydney.

The Swans confirmed their interest in Langdon publicly on Wednesday.

“He flew to Sydney yesterday and had a medical,” Sydney’s Head of Football Tom Harley said.

“We spoke to (Magpies list manager) Ned Guy about that on Monday, so we’ve been transparent with Collingwood.

“I think the incumbent club’s always got the whip hand in that sense. We’re just waiting for the finer details from that medical at this stage.”