The Canadian men opened Friday with a 28-12 win over unheralded Belgium but faced stiffer opposition Saturday, losing 24-19 to Samoa and 45-0 to Fiji.
Samoa took advantage of Canadian errors to jump into a 24-7 lead before late tries by Justin Douglas and Liam Underwood narrowed the deficit. Mike Scholz also scored a try for Canada. Fiji then ran in seven straight tries against Canada.
The Canadians will look to beat Kenya in the Bowl quarter-final Sunday.
Fiji and South Africa were the only teams to go unbeaten through pool play.
Defending champion New Zealand, meanwhile, struggled against Portugal before taking control.
New Zealand led 24-12 at the break but came within inches of losing with Portugal scrum half Nuno Guedes failing to convert his own scrambling try which had tied the scores at 24-24 in the final stages of the pool match. The final kick of the match was just wide of the uprights.
"We didn't deserve to win that match for sure," said an unhappy New Zealand coach Gordon Tietjejns. "We didn't play smart footy and made so many errors and missed so many tackles. We made it tough for ourselves."
Fiji beat minnows Belgium 38-7, but head coach Ben Ryan was far from happy with the performance.
"We didn't play with any intensity. With all respects to Belgium, we knew we were going to win but I hoped for a much better performance," Ryan said. "That was a two-out-of 10 and if we have another performance like that in the knockout stages we are going to lose."
Fiji will play England in the quarter-finals.
"Overall I'm happy. We are three out of three and got no injuries. We have done what was expected of us and on an 11-game winning streak," Ryan said. "But England are playing well and will offer us a challenge."
New Zealand will face Argentina in the quarter-finals while the other two games will pit the United States against Samoa and South Africa against Australia.
With the Olympics Race to Rio in full flow — the top four teams at the end of the nine-legged World Series gain automatic entries — winning the Hong Kong Sevens is crucial to the plans of leaders South Africa (93 points), who have never won in Hong Kong.
The Springbok Sevens have hired the services of a psychologist travelling with the team for the first time and hope they can win the mind games on Sunday.
"We are happy with the way we are going but the real test starts now," said coach Neil Powell after South Africa emerged unbeaten with pool wins over France, Argentina and Japan.
New Zealand is in second spot in the World Series on 88 points, five behind the Blitzbokke, followed by Fiji (86) and Australia (71). England are in fifth place on 68 points and will need to finish in the last four at least to keep alive their hopes of qualification.
Canada stands 13trh overall.
— With files from The Associated Press