Rafael Nadal
Rafael Nadal is yet to be truly tested at the French Open. Pictured: Spain's Rafael Nadal celebrates after victory over Argentina's Guido Pella during their men's singles second round match on day five of The Roland Garros 2018 French Open tennis tournament in Paris, May 31, 2018. ERIC FEFERBERG/AFP/Getty Images

Former No. 1 Jim Courier believes with the way Rafael Nadal is playing on clay, only his own physical issues could prevent him from extending his record to an 11th French Open win.

Nadal has suffered just one loss since returning to action during the clay-court season in April as he won titles at the Monte-Carlo Masters, Barcelona Open and the Rome Masters.

And the Spaniard currently looks near unstoppable after reaching the third round of the French Open following one of his most emphatic displays yet in his win over Argentina's Guido Pella on Thursday.

Conceding just four games in a straight-set win over the 28-year-old, Nadal is now gearing up to face France's Richard Gasquet as he looks to emerge victorious at Roland Garros yet again.

Courier lauded Nadal's achievements in the event and feels only injuries can stop him from winning his first Grand Slam of the year as they have been a recurring theme throughout his career.

A leg injury saw him withdraw from his quarterfinal tie with Marin Cilic at the Australian Open in January earlier this year. He was expected back at the Mexican Open a month later only to have a recurrence of the same injury suffered in Melbourne.

"It's almost ridiculous that Nadal won this title ten times in an era made of such great champions," Courier said, as per Tennis World USA. "The fact that he plays as the best favorite for a 11th title is crazy. Who can stop him? If he is doing like this, probably only his health. In truth, I see the physical condition as his only possible issue. He already had one or two injuries this year."

Courier though, acknowledged there are some players who could cause an upset against the 31-year-old, namely the likes of Novak Djokovic, Juan Martin del Potro and Alexander Zverev.

In a bit of a surprise, however, the American feels less confident about Dominic Thiem's chances. The Austrian is the only player to defeat Nadal on clay last year and this year but Courier feels in a five-set match, he won't be able to replicate those results.

"There are just a few rivals. In the top half I only see Juan Martin del Potro, who could make him struggle a little bit," Courier explained. "In the bottom half Alexander Zverev, who got closer to the win in Rome. I am not confident about Dominic Thiem at the best of five."

"The best chance for me is Novak Djokovic. He already showed to be able to challenge Nadal on clay. But he will definitely have to improve. Since he won his 2016 French Open title and all the Grand Slam titles, he never reached his highest level again. If he does it, I trust him a lot," he added.

Djokovic will take on Spain's Roberto Bautista Agut in the third round on Friday.