Sydney Swans ruckman Sam Naismith's long-awaited return is likely to be delayed.

Naismith had a knee arthroscopy on Wednesday after experiencing pain when he increased his training load.

Swans coach John Longmire had previously said the 26-year-old would likely be ready to return within the next 5-6 weeks.

Naismith missed all of last season after rupturing his ACL in a training incident last March.

He will be temporarily sidelined from training and his return date is unclear.