BEIJING — Rafael Nadal made a successful debut in Olympic singles Monday, overcoming numerous missed chances by sweeping the final four games to beat Potito Starace of Italy 6-2, 3-6, 6-2.

Seeded second, Nadal will supplant Roger Federer atop the rankings next week, regardless of the outcome at the Olympics. Federer was to play his opening match later Monday.

Serena Williams won all four games when her match resumed after an overnight wait to complete a rain-interrupted victory over Olga Govortsova of Belarus, 6-3, 6-1.

Like Nadal, Williams was playing her first singles match at the Olympics. She won a gold medal in doubles in 2000 with her sister Venus.

No. 6 Dinara Safina of Russia won her 11th match in a row by beating Mara Santangelo of Italy 6-3, 7-6 (1). Safina has won her past two tournaments.

Nicolas Massu of Chile opened his bid to repeat as Olympic champion by beating Steve Darcis of Belgium 6-4, 7-5. Massu won the gold at Athens in both singles and doubles.

No. 7-seeded David Nalbandian of Argentina defeated Zeng Shaoxuan of China 6-2, 6-1. Chinese men finished the tournament 0-3.

Nadal struggled on the backhand side for most of his match, and shook his head or rolled his eyes when usually reliable strokes misfired.

He failed to convert seven consecutive break-point opportunities before he broke for a 4-2 lead in the final set. He erased a 15-40 deficit on his serve in the next game, then broke again for the victory.

A highlight-reel shot got him going early in the third set. Nadal sprinted into the alley near the net in pursuit of a ball and scooped a forehand winner cross-court as he braked to avoid running into the post, then fell to his back. He rose and threw a jubilant fist, leaving behind a spot in the concrete damp with his sweat.

Nadal is seeking his eighth tournament title this year. He beat Federer in the finals at the French Open and Wimbledon.