SYDNEY superstar Chloe Molloy will miss the rest of the NAB AFLW season due to an ACL injury.

One of the most recognisable athletes in the women's competition, Molloy was a late withdrawal from the Swans' clash with St Kilda on Sunday.

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The injury was initially described by Sydney as "knee soreness" about an hour before the match, with co-captain Molloy replaced by Kiara Hillier in the team.

But 45 minutes later, the Swans released a short statement confirming their worst fears for Molloy.

"We can confirm that Chloe Molloy has unfortunately sustained an ACL injury," the club said in the statement.

"Chloe and coach Scott Gowans will speak to media post-game, for now the focus is on the game against the Saints."

Molloy sustained the injury at training this week but was on hand at RSEA Park in Moorabbin to support her teammates and appeared in high spirits.

The Swans said players took to the field without knowing the full extent of Molloy's injury.

The 25-year-old is a three-time All-Australian and led the Swans' goal-kicking in her first season with the club last year after a high-profile switch from Collingwood.

Molloy is the second AFLW club captain to be sidelined with an ACL injury in a matter of days.

Port Adelaide skipper Janelle Cuthbertson was hurt during her side's win over the Western Bulldogs on Friday night and will also miss the rest of the season.