A hamstring strain has ruled Sydney captain Callum Mills out of his side's upcoming preliminary final in what is the latest blow for the Swans star.

Scans have discovered a minor hamstring strain after Mills was left hampered at training on Tuesday just 10 days out from his side's next final.

The club has confirmed Mills won't play in next Friday's preliminary final at the SCG due to the injury, with a return timeframe not yet known.

"Sydney Swans captain Callum Mills is unavailable for next Friday night's Preliminary Final after sustaining a hamstring injury at training yesterday," a club update read.

"Scans this evening confirmed a minor strain to his left hamstring, ruling Mills out of next weekend's match.

"Mills' return to play date is not yet confirmed."

The injury comes after a frustrating past 12 months for the Swans Academy product, who missed the first half of the season due to a shoulder injury sustained shortly after the end of his club's 2023 campaign.

A calf issue delayed Mills' return to the field, with his first game for 2024 not coming until Round 19.

The Swans will host a preliminary final next Friday at the SCG, with their opponent to be the winner of this week's semi-final between Port Adelaide and Hawthorn.