The United States, gold medalists four years ago, slumped to 2-0 defeat by Norway in their opening match of the Olympic women's soccer tournament on Wednesday.
Germany and Brazil, playing a rematch of last year's World Cup final which the Europeans won, drew 0-0 and hosts China beat Sweden 2-1 in the first action of the Games, two days before the official opening ceremony.
The US never recovered from a poor start in which they trailed 2-0 after only four minutes in their Group G match in Qinhuangdao, Leni Larsen Kaurin and Melissa Wiik scoring the goals for Norway.
World Player of the Year Marta produced only a few moments of inspiration for Brazil in a Group F match played before a disappointing crowd in Shenyang.
In the 11th minute she produced a superb cross, only for the unmarked Cristiane to head over.
Marta missed an excellent chance from a rebound in the second half and went close with a long-range shot and an individual effort in the closing minutes.
Germany's best opportunity fell to Sandra Smisek who headed against the crossbar in the 22nd minute.
A 72nd-minute goal from Han Duan gave China a 2-1 win over Sweden before a packed stadium in Tianjin.
Xu Yuan gave China a sixth-minute lead and Lotta Schelin equalized seven minutes before the break in the Group E match.