Lasith Malinga accepts he will be in pain for the entire World Cup.

But the Sri Lankan slinger is upbeat his rhythm is returning after undergoing ankle surgery in September.

Malinga’s unorthodox action can conjure a near-unplayable yorker, making him one of the greatest bowlers in the tournament.

The underdone paceman has delivered few of those in Sri Lanka’s opening four games of the tournament.

Malinga is still relying on pain-killing injections to make it through matches, but says he is starting to feel more comfortable at the crease.

“I really struggled after my surgery in Melbourne,” Malinga told AAP.

“There’s still pain in my ankle, but I had to get used to it.

“Because I wanted to play in this World Cup, whether that meant injections or whatever.

“It’s getting there. I don’t think I will be pain-free, but I want to get my rhythm back to perfect.”

Australia will be hoping that doesn’t happen on Sunday at the SCG.

Malinga looms as a trump card for Sri Lanka, a side who have excelled with the bat over the past fortnight but are yet to truly fire with the ball.

If the 31-year-old with the distinctive mop of hair can rediscover his best, it will be a major boost to his team’s hopes of lifting the trophy on March 29.

Mahela Jayawardene was confident it wasn’t too far away.

“He’s definitely improved,” the veteran batsman said of Malinga’s progress over the past three weeks.

“His variations are coming good; his pace has picked up.

“It’s about him having the confidence to put weight on that ankle. In the last two to three weeks, he’s got that confidence back, so the pace has built up.”

Malinga is no stranger to Australian conditions.

The right-armer played the first of his 30 Tests in Darwin, twice snaring the wicket of Darren Lehmann.

Sunday will be Malinga’s 20th ODI in Australia, including three wickets at the Gabba in 2013 when he helped roll the hosts for just 74.

The speedster also impressed during a Big Bash League stint.

Malinga noted there was plenty he could call on when coming up with plans for Australia’s star-studded XI.

But he added the best way to bring about their downfall would be to keep it simple.

“We can watch all the video in the world, but the really important thing we have to be concerned with is our strengths,” Malinga said.

“That’s how we’ll win the game.

“We’re not looking too much over their weaknesses.

“All their batsmen are really good players and in good form, but they’ve all been dismissed.

“Our bowlers just have to bowl good deliveries. We can match it with them.”

Aaron Finch suggested his side knew exactly what to expect from Malinga.

“He’s got all the tricks – great yorker, slower ball, bouncer, he can swing it as well,” Finch said.