GEELONG captain Joel Selwood will have surgery on his left ankle after scans confirmed he suffered a syndesmosis injury in Friday night's 46-point loss to Sydney.

However, the club expects the 29-year-old to be available in time for the finals in just over a month.

Selwood will miss home and away matches against Richmond, Collingwood and Greater Western Sydney in a massive blow to the Cats' top four hopes.

Geelong is currently in fourth place, a game and half clear of Port Adelaide, Sydney and the Western Bulldogs.

The Cats released a statement on Sunday evening, saying surgery was deemed the best option after "consulting with specialists in the field".

Selwood, who was on crutches over the weekend, hurt ankle in two separate incidents against the Swans.

He first rolled the outside of his ankle when he stood on teammate Zac Smith's foot in a marking contest late in the second quarter.

Selwood was unable to put weight on his left foot as he left the field in the hands of the club's medicos.

He had his ankle strapped and performed a fitness test in the rooms during the main break, before starting the third quarter on the ground.

Selwood then suffered the more severe injury to the same ankle late in the third term as his leg got caught under a Buddy Franklin tackle – this time twisting inwards – which left him hobbling at three-quarter time.

The tough skipper began the last term on the ground but was wrapped in cotton wool a few minutes later, with the club deciding to not risk him further.

Selwood has played all but one game this season, missing the round 15 draw with the Giants due to concussion he suffered a week prior against Fremantle.