Sydney's all-conquering on-ball brigade will have their new-found depth tested on Friday after All Australian midfielder Dan Hannebery was diagnosed with an ankle injury which threatens to sideline him for up to six weeks.

Hannebery has suffered what the Swans describe as a "slight syndesmosis tear" to his right ankle, which he injured while being tackled against Port Adelaide on the weekend, and will be on crutches for 10 days before beginning his rehabilitation.

Dan Hannebery has suffered an injury to his right ankle. Credit:Anthony Johnson

The Swans are hopeful Hannebery can return within four weeks, or maybe even three, but have not ruled out the prospect of it being a six-week injury.

"He's probably looking at four weeks at the moment," said Swans coach John Longmire.