Rebounding Swan Nick Blakey is set to spend the vast majority of next month on the sidelines after being diagnosed with glandular fever.

Blakey, 22, featured in all but one of Sydney's 25 fixtures along the way to a grand final birth last season, averaging 19.5 disposals and 5.2 rebound 50s each week.

The moustachioed member of the Bloods' back six will spend the next three weeks on the sidelines, acting as a sharp speedbump across the backend of his pre-season program.

"Nick Blakey has been feeling unwell and results from tests have shown he has a mild case of glandular fever," Swans head of physiotherapy and medical services Damian Raper revealed in a club statement.

"As a result, Nick will be rested for approximately three weeks before returning to training."

The son-of-a-gun now joins Ryan Clarke (hamstring), Hayden McLean (quad) and Sam Wicks (shoulder) on the injury list in the Harbour City.

Blakey's absence from the main group will likely see him miss both of Sydney's pre-season fixtures scheduled between February 24 and March 3.

The Swans will first face off against Brisbane at the club's training base in Moore Park before hosting Carlton at Blacktown International Sports Park a week later.

Although interrupting after a successful 2022 season, Blakey is likely to return for Sydney's opening home-and-away fixture against Gold Coast at Metricon Stadium on Saturday, March 18.