Rafael Nadal's participation at this summer's Paris Olympics is in doubt because of a thigh injury.
The 38-year-old - who is a 14-time champion at Roland Garros, where this summer's events are being held - has been registered to represent Spain in both the men's singles and doubles.
Nadal is scheduled to face Hungary's Marton Fucsovics in the first round of the singles on Sunday, with the winner likely to meet Novak Djokovic in round two.
A day earlier, Nadal and reigning Wimbledon champion Carlos Alcaraz are due to start their doubles campaign against Argentina's Maximo Gonzalez and Andres Molteni.
But Nadal did not train on Thursday, raising questions about his potential involvement.
Rafael Nadal is hoping to represent Spain at this summer's Olympic Games in Paris, France
Nadal pictured (left) training with Carlos Alcaraz (right) on Wednesday - but Nadal did not train on Thursday
Spanish icon Nadal (right) was pictured alongside Germany's Angelique Kerber (centre) and Great Britain's Andy Murray (left) on Thursday at the Olympics tennis draw ceremony
His coach, Carlos Moya, told radio station Onda Cero on Thursday: 'I can't say for sure that Nadal will play.
'We want to give him 48 hours to see how he is improving and how he is recovering and well, if everything goes normal and everything goes well, then on Saturday he will jump (to the court).
'He already rested on Monday, he came from a tough week in Bastad, and on Tuesday we resumed very slowly, very calm, knowing that, well, there was fatigue.
'Yesterday [Wednesday] was a very good day, both training singles in the morning and doubles in the afternoon, in the afternoon we could already feel that little problem and, well, we decided that the best and most coherent thing to do was to rest, to have treatment at the villa, to rest and give him time to recover'.
If Nadal does make it onto court with Alcaraz on Saturday, it could be that he decides to withdraw from the singles event.
That would see him follow the path taken by fellow former world No 1 Andy Murray, who plans to team up with Dan Evans in the men's doubles after pulling out of the singles.
Team GB pair Murray and Evans will face Japan's Taro Daniel and Kei Nishikori in round one.
Murray will represent Team GB exclusively in the men's doubles after pulling out of the singles
Former world No 1 Murray (right) will be partnered by Dan Evans (left) at the clay court event
Neal Skupski and Joe Salisbury will also represent Britain in the men's doubles, starting their bid for glory against Czech duo Tomas Machac and Adam Pavlasek.
Nadal and Murray are both two-time Olympic gold medalists.
Murray won singles gold at London 2012 and then again in Rio four years later.
Meanwhile, Nadal was the men's singles champion in Beijing in 2008, before he and Marc Lopez won the men's doubles in Rio.