After a gruelling bike leg spent chasing a breakaway, a top 10 wasn't even looking likely. But the 23-year-old Tasmanian put together a run leg for the ages, reeling in all but one - South African Henri Schoeman - to claim silver.

It was a brilliant performance considering the calibre of those he left in his wake.

The lead group of six - which included Brownlee brothers Alistair and Jonathan - entered the run leg 30 seconds ahead of Birtwhistle's pack.

"I honestly thought I'd be struggling to finish in the top ten or top eight," Britwhistle said when asked if he thought a medal was a realistic option as he slipped on his runners.

"Those guys up front, they're the strongest swim-bikers in the sport. In saying that, they're bloody good runners too.

"I'd say I'm probably one of the best runners in the sport.

"I thought I'd be able to close the gap, I didn't expect to pull that many back, I guess, and run my way to second."

The result went some way to making amends for the disappointment of missing out on the team for the Rio Olympics, which he admits may have come a year too soon in his development.

It also gave him bragging rights as Australia's first medallist on the Gold Coast.

For much of the race it looked like Matt Hauser - who celebrated his 20th birthday on Tuesday - was the Aussie most likely to break through for a medal.

He refused to be dropped from the lead group of six - featuring himself, the Brownlees, Schoeman, Scotland's Matt Austin and Kiwi Tayler Reid - which established a handy lead coming out of the swim leg.

Schoeman broke them early in the run, and was never headed, finishing in a time of 52 minutes 31 seconds. "I thought the guys were just starting off pretty easy and I thought I'd take an opportunity and go for it," Schoeman said of the run leg.

"At the end, the gap was getting bigger and bigger, I was really confident I'd beat the guys in my group."

The result signalled the end of an era, with injury and a poor preparation finally catching up with the Brownlees - who had both finished on the podium at every Commonwealth and Olympic Games podium since 2012.

Jonathan Brownlee fared little better, the world No.2 coming home seventh.