Defending champions New Zealand and Olympic gold medallists Fiji launched their World Cup Sevens campaigns with comfortable victories here Friday as Australia crashed out.
New Zealand, bidding to become the first team in history to claim back-to-back World Cup Sevens crowns, overpowered Russia 29-5 to book their place in the quarter-finals at AT&T Park, home of baseball's San Francisco Giants.
Fiji, the 2016 Olympic champions, meanwhile survived an early scare against a Japan side bristling with Fiji-born talent to win 35-10.
The Fijians, roared on by a vocal contingent of fans, held their nerve after trailing 7-5 at half-time to stretch away after the restart, with France-based stars Leone Nakarawa and Semi Radradra both impressing from the bench.
The Fijians will now play Argentina in Saturday's quarter-finals for a place in the last four.
Fiji coach Gareth Baber was satisfied at how his team had coped with the pressure of the tournament's new straight knockout format.
In contrast to previous years, where teams played group games before the knockout stage, this year's event is a single elimination tournament.
"You just want to win every game," Baber told AFP.
"I was pleased with the concentration levels, the focus that we had to control the game and get what we needed out of it in the second half.
"Obviously there was a couple of errors from Japan at the end but it was a very good test."
Baber also paid tribute to the way that Radradra, Nakarawa and other recent additions to the Fiji squad had fitted in.
"They're winners. And they've come into a group of boys that are also winners," Baber said.
But while Fiji and New Zealand both came through their first round tests, there was disappointment for Australia who tumbled out to France.
- 'Just unbelievable' -
France's Tavite Veredamu -- a soldier in the French Foreign Legion who was drafted into France's sevens squad last year -- scored twice in a pulsating 22-17 victory.
"It's just unbelievable," Veredamu told AFP. "We knew that we could cause a surprise here. Hopefully we can cause another surprise this weekend."
France's reward for their upset of Australia is a meeting with mighty New Zealand on Saturday in the last eight.
In other first round action on Friday, top seeds South Africa demolished Ireland 45-7 to progress to a quarter-final against Scotland.
The Scots battled into the last eight after an astonishing comeback to defeat Kenya.
The Kenyans looked to be cruising into the last eight after racing into a 26-0 lead early in the second half.
But Scotland reeled off unanswered tries from Harvey Elms, Scott Riddell and two from Jamie Farndale as well as a penalty try to seal a sensational 31-26 victory in stoppage time.
The biggest cheer of a raucous opening day watched by an estimated crowd of 25,000 came in the United States' opening win over Wales.
The host nation have emerged as a genuine force on the world sevens circuit, where they have recorded victories in London and Las Vegas in recent years.
The Americans were too powerful for an outmatched Welsh team on Friday, running out 35-0 winners.
The USA will now face England for a place in the semi-finals on Saturday. The English battled to a 19-15 win over Samoa to advance to the last eight.
In the women's tournament meanwhile, New Zealand marked themselves out as the team to beat with two emphatic wins, piling up more than 100 points without conceding a point in wins over Mexico and Ireland.
New Zealand will play the United States in Saturday's semi-finals.
Australia's women meanwhile will have a chance to avenge their men's team's defeat when they face France in the other half of the draw.
Australia progressed with wins over Papua New Guinea and Spain. France advanced to the semi-finals after beating Canada 24-19.