ADELAIDE midfielder Brad Symes is unlikely to play again this season after scans confirmed he suffered a fractured jaw in a clash with St Kilda skipper Nick Riewoldt at Etihad Stadium last Friday night.

Symes will require surgery to have a plate inserted in his jaw, and is expected to miss between four to six weeks.

Riewoldt was handed a three-match ban as a result of the incident, which took place in the first quarter of the Crows' 103-point loss to the Saints, but will miss only one match after accepting an early guilty plea.

The injury is another blow to Symes, who missed the first half of 2010 after injuring his knee in the pre-season, and has struggled to cement a position in the team this season.

Defender Matthew Jaensch (shoulder) and mature-age recruit Ian Callinan (hamstring) have also been ruled out of Showdown XXXI at AAMI Stadium on Sunday through injury.

Port Adelaide will be without first-choice players Dean Brogan (calf), Alipate Carlile (hip) and Jasper Pittard (hamstring) for the clash, but expect to regain reigning Showdown medallist Justin Westhoff from a toe complaint.