Cat Osterman won a tight pitching duel with Juri Takayama as the US softball team beat Japan 3-0 in extra innings.
Osterman won a pitching duel
Osterman struck out 11 batters in her first Olympic start, while Takayama kept the Americans hitless through the regulation seven innings.
But Japan, who had vowed revenge for a narrow 2-1 loss at the Sydney Games, tasted another bitter defeat.
"After the first couple of pitches, I thought like I was in a groove," said Osterman, who was credited with a win.
Takayama added: "This was a hard loss to take."
In other action, China rallied for four runs in the sixth inning to beat Canada 4-2, Greece defeated Italy 2-1 and Australia shut out Taiwan 1-0, handing the Taiwanese their third loss in a row