Brothers Erik and Kawika Shoji and the young U.S. men's volleyball team lost its Olympic opener in straight sets to Canada on Sunday night.
Canada won 25-23, 25-17 and 25-23.
The No. 5-ranked Americans watched as the hard-hitting and 12th-ranked Canadians celebrated at Maracanazinho arena in the first pool-play match for both countries.
Tied 23-23 in the third set, Canada held on after ending the second set on a 10-2 run.
Canada also beat the U.S. in a five-setter for the Champions Cup title in May 2015 at Detroit, before the Americans won on the way to last year's World Cup crown in Japan.
Eight of the 12 U.S. players are in their first Olympics.
It was a stunning start to the Games for the United States, which is shooting for a medal in what could be the final Olympics for veterans Reid Priddy and David Lee. Priddy is in his fourth Olympics and Lee his third.
Earlier in the day, Brazil's Bruno Rezende, Mauricio Souza and William Arjona were among the last to leave the volleyball court as many of the players took time to go through the arena and thank the fans with photos, handshakes, smiles and thumbs-up signs after winning their Olympic opener before the home crowd.
In fact, the yellow-shirted venue volunteers had to pull a handful of players to their next spot: the media mixed zone.
The host Brazilians beat Mexico 23-25, 25-19, 25-14, 25-18 and Lucas Saatkamp's winning kill sent the crowd into an absolute frenzy as players threw their arms up in celebration.
The second day of women's volleyball preliminaries begins at 8:30 a.m. ET Monday.
After a day off Monday, the men's teams resume play again Tuesday morning.