Number two seed Agnieszka Radwanska made a shock first round exit from the women's singles on Sunday while fellow Wimbledon runner-up Britain's Andy Murray made light work of his match against Stanislas Wawrinka to advance to the second round.
Poland's Radwanska, playing under the Centre Court roof due to sporadic heavy rain showers which prevented play on the outside courts for most of the afternoon, crashed out 7-5, 6-7, 6-4 to world number 24 Julia Goerges.
"I played pretty aggressive and served well," said the German, who had lost twice to Radwanska this year.
"I know if I play well it's dangerous for anyone and it was today, a lucky day."
Fourth seed Murray, back on Centre Court three weeks to the day after losing the Wimbledon final against Roger Federer, made a strong start to his singles medal campaign with a 6-3, 6-3 win over Federer's doubles partner Wawrinka.
The win means Murray, who with his brother Jamie was knocked out of the men's doubles on Saturday by Austria's Juergen Melzer and Alexander Peya, has already improved on his Olympic debut in Beijing where he suffered a first round singles defeat to Taiwan's lowly ranked Lu Yen-hsun in straight sets.
"I know how much that loss hurt me and I wanted to come here best prepared as I could be and today was a good start," the 25-year-old Scot, whose win was met with a deafening eruption of noise from the home crowd, said after the match.
Wawrinka can now concentrate on defending his Beijing doubles medal with Federer, who was on court to cheer him on, although the pair will have to wait until at least Monday after their opening match was one of 10 postponed from Sunday's schedule of play due to the rain.
In only the third of the day's completed matches, former Wimbledon winner Russia's Maria Sharapova, making her Olympic debut, marched into the second round with a 6-2, 6-0 win over Israel's Shahar Peer.
On Court One, men's second seed an Beijing bronze medallist Novak Djokovic had reached a first set tie-break against Italy's Fabio Fognini before rain suspended play at seven points apiece.
When the match finally resumed hours later, with groundstaff having taken the protective covers off the court several times during the afternoon only to have to cover them over again as the rain restarted, Fognini quickly wrapped up the set to take the lead against the Serbian.
If the rain holds off, three-time gold medallist Venus Williams is due to face Italy's Sara Errani in the second match on Court One.
Photograph: Elise Amendola/AP