Grand Slam record-breakers Novak Djokovic and Rafael Nadal were placed on a second-round collision course as the draw was made for the tennis competition at Roland Garros.
The Spanish women's football team are appearing at an Olympics for the first time, led by 2023 world player of the year Aitana Bonmati, and face Japan.
Scandal-hit reigning champions Canada play New Zealand without their coach Bev Priestman after incidents of spying on their opponents' training sessions with drones.
Canada's assistant coach and an analyst were dismissed from the Olympics for their part in the incidents and the analyst was given a suspended eight-month prison sentence by a French court.
Priestman apologised to New Zealand and said it would not be appropriate for her to be on the bench on Thursday.
It all adds up to a difficult start for the football at the Games after a chaotic end to Argentina's match against Morocco, when the men's competition kicked off on Wednesday.
Morocco beat the two-time Olympic champions 2-1 in Saint-Etienne, but only after a late equaliser for the South American side was disallowed and the final minutes took place in an empty stadium following crowd trouble.
"It is a disgrace that this should happen and poison the tournament," said Argentina coach Javier Mascherano.
Israel's footballers later drew 1-1 with Mali on Wednesday under the watchful eye of 1,000 police officers, with authorities erecting an "anti-terrorist perimeter" around the Parc des Princes stadium.
Israel's participation at the Olympics has been a key talking point following calls from the Palestine Olympic Committee and Iran for the country to be excluded over the Gaza war.
Some Palestinian and Israeli flags were flown, with angry words exchanged among fans at the Parc des Princes.
French interior minister Gerald Darmanin said however "there have been no security problems to our knowledge".
'End the feud'
US Olympic chiefs on Thursday called for an end to the feud between American anti-doping officials and the World Anti-Doping Agency (WADA) after fresh verbal sparring.
Gene Sykes, the chairman of the US Olympic and Paralympic Committee, said WADA and the US Anti-Doping Agency had been "playing ping pong with media bullets" since revelations about a 2021 doping scandal involving Chinese swimmers emerged.
The acrimony between the two bodies flared again on Wednesday, with the International Olympic Committee warning US officials they could be stripped of the 2034 Winter Olympics in Salt Lake City if WADA was not respected as the "supreme authority" of the anti-doping movement.
"What we want to do is to cool the tempers and find a way for these organisations to constructively work better together," Sykes told a press conference.
The tennis draw threw up a mouthwatering potential second-round tie between 2008 gold medallist Nadal and 24-time Grand Slam champion Djokovic, while two-time Olympic champion Andy Murray withdrew from the singles.
"I am excited for this duel in the second round, and I will give it my all," said Djokovic, who has faced Nadal 59 times over the past 18 years.
US gymnastics superstar Simone Biles got her first taste of the Bercy Arena as she trained ahead of the start of competition at the weekend.
Biles is strongly tipped to add to her cache of four Olympic golds at the Paris Games after a tumultuous Tokyo campaign, when she withdrew from most of her events as she battled the dangerous and disorientating "twisties".
Preparations for Friday's historic opening ceremony were in full swing, with an unprecedented security operation for the athletes' parade along the River Seine.
Around 6,000-7,000 athletes are set to sail down a six-kilometre (four-mile) stretch of the river towards the Eiffel Tower, on 85 barges and boats.
The line-up of performers is a closely guarded secret but US pop star Lady Gaga is rumoured to be among them.
