Clarke will be fitness tested on the morning of the match after he twisted his ankle at training on Tuesday.
Australia's specialist Twenty20 captain George Bailey is waiting to take over from Clarke, if the skipper is ruled unfit.
Clarke rolled his ankle during a team warm-up in Hobart on Tuesday morning.
He reportedly spent the rest of the day with constant ice treatment and desperate physiotherapy in a bid to reduce swelling so he could possibly lead his side within 24 hours of suffering his injury.
It appears a growing likelihood that Clarke will miss the clash after the current world number-one ranked batsman sat out the first two games of the series to rest after a hectic summer of Test commitments.
If Clarke is deemed unfit it is likely that an all-rounder will replace the batting specialist and skipper.
Clarke is the nation's most accomplished batsman in a struggling limited-overs outfit that has managed scores of 305 in the series opener at the MCG, but then 170 in Adelaide, just 74 in Brisbane and only scrambled to 9-222 with a tail-end cameo 52 not out from bowler Mitchell Starc at the SCG on Sunday.
Limited-overs middle-order star David Hussey or vice-captain George Bailey are expected to move to Clarke's number three spot with all-rounder Glenn Maxwell to assume a more specialist batting role ahead of wicketkeeper Matthew Wade.
Maxwell averages 27.40 from his six ODIs while the other member of Australia's 13-man squad, Ben Cutting, is a pace bowler and lower-order hitter.
Bailey would take of captaincy on his home turf for a first time.
The looming stand-in skipper revealed on Tuesday that Clarke would be given every chance to confirm his recovery in time to play.
"He will obviously be given right up to the toss tomorrow to prove he is right to go," Bailey said on Tuesday.
"There will be a little bit of pain but, if he is 100 per cent, he will play."
"If it is swinging and seaming a little bit early and it does happen to be a good batting wicket, then hopefully you make the most of that."
Bailey said the inexperienced and changing Australian line-up had been dealt a lesson in the rigours of international cricket.
"The change from domestically, where you might play a good side once or twice a year ... whereas you're coming up against world-class players day-in, day-out here," he said.
"That challenge doesn't go away, particularly with a team like Sri Lanka which has such a great one-day record."
Australian squad: Michael Clarke (capt), George Bailey, Ben Cutting, Xavier Doherty, Moises Henriques, Phil Hughes, David Hussey, Mitchell Johnson, Glenn Maxwell, Clint McKay, Mitchell Starc, Matthew Wade, David Warner.
Additional reporting from AAP