GEELONG has suffered a blow ahead of its crunch game against the Western Bulldogs with in-form midfielder Cameron Guthrie ruled out with illness.

Guthrie was replaced by emergency Cory Gregson when the Cats filed their final team 90 minutes ahead of Saturday night's game at Etihad Stadium.

The Western Bulldogs made no late changes to their selected side.

Guthrie has been one of Geelong's most consistent players this season, averaging almost 24 possessions a game over the first 12 rounds.