One down, six to go at Olympics for US swim star Dressel
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The 24-year-old limbered up for his three individual events with a powerful 47.26sec opening leg to set up his team-mates, who brought it home in the third-fastest time ever.
Zach Apple touched in 3:08.97 after Dressel's start followed by sizzling swims from Blake Pieroni and Bowen Becker, with Italy (3:10.11) and Australia (3:10.22) in the minor placings.
The United States, who have won 10 of the past 13 men's 4x100m relay golds, were competing without Michael Phelps for the first time since the 2000 Sydney Olympics, and Dressel acknowledged they had a point to prove.
"It feels great," he said. "We knew we had a huge target on our back. It feels nice, I'd say we dominated that pretty well.
"We're never going to doubt ourselves, that's how Team USA works. We had a couple of people rule us out and we're never going to take that."
"Everyone did their job," he added. "It's a relay for a reason, there's four guys for a reason, it's certainly not just one guy."
It was a perfect Tokyo bow for Dressel, who will tackle three individual events -- the 50m and 100m freestyle and the 100m butterfly.
He is the two-time reigning world champion in all three and the 100m fly world record-holder.
There are also a possible four relays on his card as he stands poised to cement an Olympic legacy that began when he earned two relay golds in Rio in 2016.
Phelp's dazzling eight golds in eight events at the 2008 Beijing Olympics eclipsed the record seven swimming golds won by Mark Spitz in Munich in 1972.
American Matt Biondi won five golds, a silver and a bronze in Seoul in 1988.