Spain's Carlos Alcaraz will join 24-time Grand Slam champion Novak Djokovic in the Olympic men's singles quarter-finals.
But Alcaraz and 14-time French Open champion Rafael Nadal were beaten in the men's doubles by USA's Austin Krajicek and Rajeev Ram - losing 6-2 6-4.
Reigning French Open champion Alcaraz defeated Russian Roman Safiullin, who is competing as an Individual Neutral Athlete, 6-4 6-2.
Earlier, Djokovic beat Germany's Dominik Koepfer 7-5 6-3 in very humid conditions, as the Serb continues his quest for the Olympic men's singles gold that has so far eluded him.
"I'm soaking wet, honestly," Djokovic said moments after his win.