SYDNEY captain Josh Kennedy will be in a race against time to prove he's recovered from back spasms ahead of next week's clash with Gold Coast.

Kennedy failed to return after half-time in the Swan's come-from-behind win over North Melbourne on Sunday.

The skipper pulled up short while attempting to tackle Roos youngster Luke Davies-Uniacke, before coming to the bench in instant agony.

Requiring assistance to get to his feet after receiving work from Swans' trainers, Kennedy took painkillers before being further assessed during the main break.

Coach John Longmire conceded Kennedy was in doubt ahead of the clash with the Suns at the SCG next Saturday.

"It tightened up, (I'm) not sure how he'd go going into a six-day break," Longmire said.

"He's reasonably confident, he's had it before, it settles down after a couple of days. We'll have to wait and see."

The loss of Kennedy further exposed the Swans' youngsters on Sunday with Jarrad McVeigh (collarbone), Dan Hannebery (groin) and Kieren Jack (knee) already sidelined.