Nadal, who faces Hungary's Marton Fucsovics in the first round, won his opening doubles alongside Carlos Alcaraz on Saturday, but had his right thigh heavily bandaged.
"The issue of the bandage is cumbersome, but it is also an issue of prevention," said Spain captain David Ferrer.
"We will see when the match is over how it evolves but the important thing is that today Rafa has warmed up, that he is ready to play."
On Saturday, Nadal had cast doubt on his participation in the singles, insisting he would "make the smartest decision that I can to have the best chance of bringing a medal home".
Nadal, a singles gold medallist at the 2008 Beijing Olympics and doubles title-winner at Rio four years later, is playing just his seventh tournament of 2024.
Before suffering a thigh injury in training in Paris, he had battled a hip problem and sat out Wimbledon.
Nadal has won 14 of his 22 Grand Slam titles in Paris but, at 38, time is ticking for the Spaniard, who this year suffered his earliest exit from the French Open.
He is unseeded at the Games and a win over 83rd-ranked Fucsovics would pit him against top seed Djokovic in the second round, in what would be the pair's 60th meeting.
They have played 10 times at Roland Garros.
"Roland Garros is the most special place in the world of tennis for me," said Nadal.
Later Sunday, former world number one and three-time Grand Slam title winner Andy Murray plays what could be the final match of his career.
Pull-outs
The 37-year-old has already confirmed that the Paris Olympics will be his last tournament.
A two-time gold medallist in Olympic singles in 2012 and 2016, Murray is partnering Dan Evans in the doubles.
"The Olympics are incredibly special for me, had some amazing memories on the court in London in 2012," said Murray who underwent surgery to remove a cyst on his back on the eve of Wimbledon.
"Playing at home and winning medals was unbelievable. I am happy to do it one more time to compete for my country.
Djokovic dropped just one game in his opening win at the Olympics on Saturday against unranked Matthew Ebden.
The Australian doubles specialist was called into the singles draw as an alternate following a series of last-minute withdrawals which included world number one Jannik Sinner.
Djokovic raced to victory in just 53 minutes against a player who had not competed in a singles match for two years.
"I don't think it's a good image for the sport," said Djokovic.
On Sunday, that image took another battering when three more players dropped out of the first-round draw.
Australia's sixth-ranked Alex de Minaur withdrew after failing to recover fully from a hip injury at Wimbledon although he remains committed to doubles.
De Minaur has been replaced by unranked Francisco Cabral of Portugal.
Britain's Cameron Norrie, a former top-10 player, scratched from his clash with world number 27 Tallon Griekspoor of the Netherlands.
Norrie's place in the draw has gone to Petros Tsitsipas, the unranked Greek who is the younger brother of world number 12 Stefanos Tsitsipas.
In the women's singles, 47th-ranked Anhelina Kalinina pulled out, to be replaced by Australia's world number 164 Olivia Gadecki.
Among early winners Sunday were eighth-ranked Maria Sakkari of Greece, who dropped just one game against Danka Kovinic, the world 668 from Montenegro.
American world number nine Danielle Collins progressed when her German opponent Laura Siegemund retired with illness in the second set of their opener.
