CALLUM Mills has suffered more September heartbreak, with scans confirming the Sydney captain has torn his anterior cruciate ligament.

The defender could also potentially miss the entire 2027 season after he went down with a serious knee injury during Sydney’s 53-point upset of Brisbane.

Mills' right knee gave way as he attempted to corral Will Ashcroft near the boundary late in the first quarter after an understrength Swans outfit burst to a 40-8 lead.

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Horror Swans scenes as skipper suffers worrying knee injury

Sydney is dealt a massive blow as captain Callum Mills is helped from the field after suffering a knee injury

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Swans coach Dean Cox was already expecting the worst in the aftermath, with scans on Monday confirming the injury.

The Swans are yet to decide who will captain the side for the rest of this season, with Mills absent and vice-captain Isaac Heeney suspended. Former skipper Dane Rampe and star midfielder Errol Gulden are the most likely options in the frame.

Mills will meet with a specialist to determine a date for surgery.

It is the latest setback for the luckless 29-year-old, who missed the Swans' 2024 Grand Final loss due to a hamstring strain.

Mills had played just seven games in 2024 after hurting a shoulder in a 'Mad Monday' wrestling contest with a teammate.

This year was the first time the defender had played more than 20 games since Sydney's 2022 Grand Final run.

The upset victory against Brisbane followed a tumultuous few weeks in the fallout from the Pullman Hotel scandal.

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Mills has earned significant praise for leading the Swans through the turmoil, which past players have admitted shattered the club's famed "Bloods culture''.

Cox's selection conundrum for the upcoming preliminary final is further complicated with key forward Joel Amartey (Achilles) and winger Justin McInerney (hamstring) nearing full fitness.

Hayden McLean - playing as cover for Amartey - slotted three majors against the Lions, with fellow talls Charlie Curnow (five goals) and Logan McDonald (six) also busy.