Rafael Nadal may be facing another injury setback at the Paris Olympic Games after his coach warned over the Spaniard's fitness.

The 22-time major champion is widely expected to retire at the end of this year, though is preparing for a final swansong at Roland-Garros, where he has won 14 titles.

Nadal is set to play in the singles and doubles tournaments of the Olympics, partnering current French Open and Wimbledon champion Carlos Alcaraz for the latter competition.

Yet his participation has become doubtful after coach Carlos Moya confirmed Nadal had cancelled his training session on Thursday due to a hamstring issue.

"It was a setback and we decided that today Rafa would rest and not train to recover," Moya said, as quoted by Spanish journalist Rafael Plaza.

"We are going to give ourselves 48 hours, we have to wait."

The 38-year-old is reportedly feeling soreness in both his left and right hamstring having pulled out of a scheduled practice session with Alexander Zverev.

Alcaraz had been partnering Nadal throughout the week during training on the clay courts of Paris, though the veteran's feature has now been thrown under a cloud of doubt.

Nadal is one of just two players to have won Olympic gold in both singles and doubles since the sport returned to the Games in 1988, doing so at Beijing 2008 (singles) and Rio 2016 (doubles).

In the singles in the French capital, Nadal has been drawn against Hungary's Marton Fucsovics in the opening round, and the prize could be a second-round date with long-term rival Novak Djokovic.