RIO DE JANEIRO - Five facts on the Olympic Games tennis tournament:
Roger Federer has fond memories of the Olympics winning doubles gold in Beijing in 2008 and a silver in singles in London four years later
+ Novak Djokovic, Andy Murray, Roger Federer and Rafael Nadal, the big four of the men's game, and Serena Williams, the undisputed superstar of the women's tour, will comfortably be amongst the medal favourites in Rio. Murray and Williams are the defending champions while Nadal took gold in Beijing in 2008. However, there have been a number of high-profile pull-outs with top ten players Milos Raonic, Tomas Berdych and Dominic Thiem opting not to play either over fears of the Zika virus or scheduling complaints ahead of the US Open. Maria Sharapova is also missing as she serves a drugs ban while Victoria Azarenka is expecting a baby and will sit out the rest of the year. Some players are unhappy that there are no ranking points or prize money up for grabs. Latvia's Ernests Gulbis refused to play, blasting the event as "tennis tourism".
+ Irish-born John Pius Boland, representing Great Britain, was the first tennis gold medallist at the Olympics in 1896 in Athens. Boland was a late entry into the event after originally going to Greece to visit a friend. He also won the doubles gold with a German partner as part of a mixed team. Boland was an Irish nationalist politician who backed Home Rule for Ireland and sat in the British House of Commons from 1900-1918.
+ Tennis was left off the Olympic programme from 1924 until 1988 after a row over allowing professional players to take part. When the sport returned to the schedule in Seoul in 1988, the men's singles gold was won by Czech player Miroslav Mecir. Other surprise gold medallists have been Marc Rosset of Switzerland in 1992 in Barcelona and Nicolas Massu of Chile at the 2004 Athens Games. Massu had also partnered Fernando Gonzalez to the men's doubles title in Greece, giving Chile its first ever gold at an Olympics.
+ Five golds are up for grabs in Rio -- men's and women's singles and doubles and mixed doubles. The event takes place at the purpose-built centre in the Barra Olympic Park with a main court, named after Brazilian tennis veteran Maria Bueno, holding 10,000 fans.
+ Federer has fond memories of the Olympics. He won a doubles gold medal with Stan Wawrinka in Beijing in 2008 and a silver in singles in London four years later. He also met his wife at the 2000 Sydney Olympics -- Mirka Vavrinec was also competing for Switzerland. A foot injury led to her retirement from the sport in 2002.