Australia’s world record mixed relay team have sensationally failed to qualify for the final at the world championships in Singapore.

The Aussies were the overwhelming favourites, having won gold in the previous two editions and setting world records both times.

But there will be no medal this time after a decision to rest superstars Mollie O’Callaghan and Kyle Chalmers backfired spectacularly.

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The team of Kai Taylor, Max Giuliani, Hannah Casey and Milla Jansen was still expected to qualify for the final, but they bombed out in the heats.

They could only manage the 11th fastest time (3:25.15) to fall short of the eighth-fastest Canada (3:24.95).

Coaches could be seen shaking their head in disbelief at the result.

Adding insult to the result, Australia’s world record was broken by USA in the final.

The Americans touched in a time of 3:18.48 to set the new mark.

O’Callaghan will have to wait until at least Sunday to win a record-breaking 12th world championship gold medal.

She remains tied with Ian Thorpe on 11 for the most by an Australian.

The superstar will be back in the pool on Sunday for the women’s 4x100m medley relay.

Meanwhile, Cam McEvoy carved more slices of swimming history with a powerhouse victory in the men’s 50m freestyle at the world titles.

McEvoy, 31, triumphed on Saturday night in Singapore to become Australia’s oldest gold medallist at a swimming world championships.

His feat overshadowed fellow Australian Kaylee McKeown completing her golden backstroke double with a victory over 200m.

The dual delights lifted the Dolphins to top of the medal table with seven golds, one more than the United States as competition continued on the penultimate night.

Exactly 12 months after both won Olympic gold in the events, the repeat was particularly compelling for McEvoy, the first Australian man to twice win 50m freestyle world titles.

Following his 2023 victory in Japan and silver last year in Qatar, McEvoy clocked 21.14 seconds in Singapore to prevail ahead of Great Britain’s Ben Proud (21.26) and American Jack Alexy (21.46).

McKeown enhanced her status as the world’s best female backstroker with her 200m gold medal, which follows her earlier win over 100m.

The Queenslander was challenged by American Regan Smith but touched first in two minutes 03.33 seconds, 0.96 seconds ahead of her rival.

Also Saturday night, Alexandria Perkins added to Australia’s medal tally with silver in the women’s 50m butterfly.

The 25-year-old clocked 25.31 to finish behind American Gretchen Walsh (24.83) while Australia’s Lily Price (25.61) was sixth.