Sydney's promising start to the AFL season may have come at a significant cost with injuries to Stephen Doyle and Daryn Cresswell.

The Swans said Doyle had suffered a surface fracture to the back of his right kneecap.

The 203cm ruck-forward option will undergo an arthroscope on Wednesday morning to determine his exact prognosis.

Speaking after his side's 74-point thumping of Carlton in Sydney on Saturday night, Swans coach Paul Roos was pleased he was able to use Doyle's height effectively in attack.

The 21-year-old tall kicked two goals as Sydney streamed away in the second quarter before leaving the ground with the injury.

He took no further part in the game.

Doyle played just nine matches last season, with an ankle injury he suffered in round 15 causing him to miss five weeks.

Veteran midfielder Cresswell will miss up to four weeks with a calf strain suffered during the game against the Blues.

In an indication he is nearing a return from a knee injury, the Swans listed Michael O'Loughlin for a fitness test.

Andrew Schauble will also undergo a fitness test after missing the match against Carlton with a quadriceps problem.

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