Britain's Andy Murray enjoyed a routine win over Argentina's Juan Monaco to ease into the third round of the tennis tournament at the Rio Games on Tuesday, while Spain's world number nine David Ferrer was knocked out.
Murray, who won singles gold at the London Games, outclassed Monaco 6-3 6-1 in just over an hour and will next face either France's Benoit Paire or Italy's Fabio Fognini.
"I played pretty well, hit the ball good from the back of the court, not many unforced errors. It was a good match," said Murray, who is favourite to take gold after Serbia's world number one Novak Djokovic was eliminated in the first round.
Earlier, Russia's Evgeny Donskoy edged 34-year-old Ferrer in three tense sets. Donskoy, ranked 84 in the world, upset former French Open finalist Ferrer 3-6, 7-6(1), 7-5.
"In important moments he played more aggressively than me," said Ferrer, who conceded this may be his last Olympics.
Meanwhile, Serb Novak Djokovic’s Rio Olympics campaign came to a screeching halt early Tuesday morning following his loss in the men’s doubles.
Brazilian duo Marcelo Melo and Bruno Soares beat Novak Djokovic-Nenad Zimonjic 6-4, 6-4.
Spain's campaign was on track after Marc Lopez and Rafael Nadal beat Argentine pair Juan Martin Del Potro and Maximo Gonzalez 6-3, 5-7, 6-2.
In the women's tournament, American world number nine Madison Keys reached the quarter-finals after outlasting Spain's Carla Suarez Navarro 6-3, 3-6, 6-3.
Keys struggled to find her rhythm but in the end her powerful strokes proved too much for the 5 foot 4" Navarro, who has one of the best one-handed backhands in women's tennis.
"It was a really tough match," said Keys, who will now face either Italy's Sara Errani or Russia's Daria Kasatkina.
French Open champion Muguruza crashes out
Meanwhile, Puerto Rico's Monica Puig collapsed in tears of joy after her shock 6-1 6-1 win over Spain's French Open champion Garbine Muguruza.
Puig, ranked 34, downed world number three Muguruza in just over an hour and will play Germany's Laura Siegemund in the quarter-finals.
Men's singles round 2 results from Monday
4-Kei Nishikori (Japan) beat John Millman (Australia) 7-6(4), 6-4; 6-Gael Monfils (France) beat Rogerio Dutra Silva (Brazil) 6-2, 6-4; 9-Marin Cilic (Croatia) beat Radu Albot (Moldova) 6-3, 6-4; Gilles Muller (Luxembourg) beat 5-Jo-Wilfried Tsonga (France) 6-4, 6-3; Juan Martin Del Potro (Argentina) beat Joao Sousa (Portugal) 6-3, 1-6, 6-3; 10-Roberto Bautista (Spain) beat Paolo Lorenzi (Italy) 7-6(2), 6-2; Taro Daniel (Japan) beat Kyle Edmund (Britain) 6-4, 7-5; Andrej Martin (Slovakia) beat 13-Philipp Kohlschreiber (Germany) walkover.
Men's doubles round 2 results on Monday
Marcelo Melo/Bruno Soares (Brazil) beat Novak Djokovic/Nenad Zimonjic (Serbia) 6-4, 6-4; Marc Lopez/Rafa Nadal (Spain) beat Juan Martin Del Potro/Maximo Gonzalez (Argentina) 6-3, 5-7, 6-2; Oliver Marach/Alexander Peya (Austria) beat Brian Baker/Rajeev Ram 6-4, 6-7(2), 6-3; Fabio Fognini/Andreas Seppi (Italy) beat Thomaz Bellucci/Andre Sa (Brazil) 5-7, 7-5, 6-3; 7-Daniel Nestor/Vasek Pospisil (Canada) beat Gastao Elias/Joao Sousa (Portugal) 6-1, 6-4; Roberto Bautista/David Ferrer (Spain) beat Lukasz Kubot/Marcin Matkowski (Poland) 6-3, 7-6(5); Steve Johnson/Jack Sock (US) beat Juan Sebastian Cabal/Robert Farah (Colombia) 6-4, 7-6(1); Florin Mergea/Horia Tecau (Romania) beat Santiago Gonzalez/Miguel Angel Reyes (Mexico) 6-3, 7-6(9).