London: Wimbledon champions Serena Williams and Roger Federer are in action on the opening day of the Olympic tennis tournament on Saturday, returning to the centre court just three weeks after their triumphs.
Williams faces Serbia's Jelena Jankovic in the second match on the 15,000 capacity court and is followed by Federer against Colombia's Alejandro Falla.
In the opening match, sixth seed Czech Tomas Berdych will play Belgium's Steve Darcis.
Federer's doubles partner Stanislas Wawrinka, and fellow flag bearers including Serbia's Novak Djokovic, Russia's Maria Sharapova and Wimbledon runner-up Poland's Agnieszka Radwanska have avoided an early start after Friday's late night opening ceremony, all beginning their first round matches on Sunday.
In the doubles, number one seeds American brothers Mike and Bob Bryan will play Brazil's Thomaz Bellucci and Andre Sa on Court 14.