London - World No 1 Roger Federer will begin his Olympic campaign against Alejandro Falla, the unheralded Colombian who almost humiliated the great Swiss at Wimbledon in 2010.
Federer, who won a seventh Wimbledon title earlier this month, had to come back from two sets to love down at the All England Club to beat Falla in the first round two years ago with the Colombian losing his nerve on Centre Court when he served for the match at 5-4 in the fourth set.
Top-seed Federer, who is appearing at his fourth Olympics, has been placed in the same half of the draw as fourth seed David Ferrer, who will play Vasek Pospisil of Canada.
"Federer is the favourite whenever he plays here," said Falla.
"I know him well and he knows me well, too. I'm going to have to play my best if I am going to have a chance to win this match but he's Roger and he's just won Wimbledon for the seventh year here."
Second seed Novak Djokovic, the 2008 Beijing Olympics bronze medallist, will challenge Fabio Fognini of Italy in the first round.
Djokovic is in the same half of the draw as third-seeded Briton Andy Murray, who faces Stanislas Wawrinka of Switzerland.
Wawrinka partnered Federer to the doubles gold medal in Beijing in 2008.
Fifth seed Jo-Wilfried Tsonga of France will meet Brazil's Thomaz Bellucci, the recent Gstaad Open winner.
Missing from the men's draw is defending champion Rafael Nadal who pulled out of the tournament through injury.
In the women's singles, the Williams sisters both face tricky opponents in the first round.
Wimbledon champion Serena, seeded four, plays Serbia's Jelena Jankovic while Venus tackles Italy's ninth seed Sara Errani, the French Open runner-up.
Serena and Venus are two-time doubles gold medallists, while Venus also won the singles gold medal in Sydney in 2000.
Top seed Victoria Azarenka of Belarus is up against Romania's Irina-Camelia Begu, second-seeded Pole Agnieszka Radwanska faces Germany's Julia Goerges.
Third seeded Russian, Maria Sharapova, the 2004 Wimbledon champion, plays Shahar Peer of Israel.
In total, 44 countries are being represented at The All England Club.
There is a 64-draw for the men's and women's singles, with 16 players seeded in each event, and a 32-draw for the men's and women's doubles, with eight teams seeded in each event.
Mixed doubles, which is making a return to the Olympics as a medal sport for the first time since the Paris Games of 1924, will have a 16-draw, with four teams seeded.
The draw for the mixed doubles is being held midway through the tennis event on July 31.