Marcus Stoinis provides the spark to light fire under Australia's title defence

When sub fielder Ashen Bandara took a well-balanced catch on the boundary to dismiss Glenn Maxwell, making amends for dropping struggling skipper Aaron Finch on the previous delivery, Sri Lanka could sniff a major upset.

With their title defence on home soil wobbling, Australia's T20 World Cup campaign was in the balance. Well past midnight on the country's east coast, due to a 7pm start time in Perth which contributed to a modest Optus Stadium crowd of 25,000, a lacklustre Australia were on the brink of being knocked out with most of their supporters sound asleep.

Maxwell, for a while mired in a rut, had attempted to kick-start an Australia side who, for the first time in T20Is, didn't hit a boundary during the powerplay as Finch grew increasingly frustrated with every mis-hit.

Maxwell counterattacked Sri Lanka's talismanic wristspinner Wanindu Harasanga in the 10th over, highlighted by a couple of swiped sixes, but fell with Australia 89 for 3 in the 13th over as the 159 target looked a fair way off. A win was suddenly no certainty, let alone improving their eyesore of a net run-rate which took a pounding after their disastrous opening 89-run defeat to New Zealand.

Enter, Marcus Stoinis. He's a local lad but doesn't quite get the adulation of the Optus Stadium faithful, being a stalwart in the BBL for Melbourne Stars. Out west, they're bred parochial, which helps explain why Western Australia's hard border was so popular among locals.

Recently sidelined with a side strain and in and out of form since his heroics at last year's T20 World Cup, Stoinis has been somewhat overshadowed amid Australia's slew of big-hitters of late, with newcomer Tim David hogging most of the attention.

But in just 18 deliveries, marked by six monstrous sixes at a vast ground which mirrors the MCG for dimensions, Stoinis issued a reminder of his ability to hit a long ball as he single-handedly revived Australia's campaign and provided a much-needed nudge to Australia's net run-rate.

He modestly later self-described his match-turning knock as "good slogging", but that did little justice to his targeted assault - particularly on Sri Lanka's spinners - as he hit the fastest T20I half-century for Australia, and the joint-second-fastest at a T20 World Cup.

Stoinis' batting bravado was in contrast to how he felt when he came to the crease. "I was actually quite nervous to be honest," he revealed. "The intention was to just go put an impact on the game and probably provide a bit of energy for the boys and get a spark going."

With every massive six, a fired-up Stoinis was animated in an attempt to light a fuse under Australia. But it didn't rub off on Finch, whose struggles were fortunately papered over by the fireworks at the other end.

Finch made just 31 off 42, with just one boundary, and particularly struggled against hostile quick Lahiru Kumara, who extracted plenty of seam and sharp bounce in favourable conditions.

"That new ball was doing a lot. It was definitely the hardest time to bat," Stoinis said when asked about Finch's struggles. "It's just important that he saw that through and was there to hit the winning runs."

Stoinis' pyrotechnics spared a lethargic Australia's blushes. Earlier, they had put in a ragged effort with the ball exacerbated by conceding 24 extras - their highest number since 2007, when they were barely taking the format seriously.

Pat Cummins, Josh Hazlewood and Mitchell Starc, who was held back until the fifth over, predictably bowled short of a length but weren't able to tear through the adventurous Sri Lankan batting order. Cummins leaked 20 runs in the final over, as his struggles at the death continued, in consecutive sub-par performances from him to start the tournament.

"I don't think we felt flat," Stoinis said about Australia's bowling and fielding. "It felt like we bowled pretty well... there were a few balls up in the air that fell in gaps. There's definitely things we can tidy up... three or four balls in the game, which could be the difference of 18 runs. It's the little things we will review."

Australia also had to make a late change after legspinner Adam Zampa tested positive for Covid-19 - though his replacement Ashton Agar used his local expertise to good use by bowling a back of a length to force Sri Lanka to hit to the longer boundaries square.

"It's just team balance that keeps him out of the team," Stoinis said of Agar. "I think it was an easier option for him [Zampa] to get better when you have got someone like Ash in the wings."

Flexing figuratively and literally, the muscular Stoinis has helped set up a MCG blockbuster against England with everything to play for. "The backs are still against the wall I think," Stoinis said. "We'll take the game on. It's going to be really important for us."