Dominic Thiem could be Rafael Nadal's biggest test at Roland Garros if well: Alex Corretja

Former World No. 2 Alex Corretja believes Dominic Thiem can provide the toughest challenge to Rafael Nadal at this year's Roland Garros, provided the Austrian is in good shape mentally and physically.

Dominic Thiem has established himself as one of the best claycourters on tour after Rafael Nadal and is widely tipped to be the player to end the Spaniard's dominance in Paris.

Given the Austrian's recent struggles, however, it seems unlikely that Thiem will pose much of a challenge to the 13-time champion this year.

Alex Corretja, a two-time French Open runner-up, believes Dominic Thiem still has the ability to test Rafael Nadal on the Parisian claycourts. Speaking on Eurosport, Corretja explained that the Austrian's game is well-rounded, which helps him nullify some of Nadal's key weapons on the red dirt.

"If Thiem is well, then he is probably the one that Rafa can suffer the most against on clay because of the styles of games," Corretja said. "He has got a good forehand, a good backhand, a good serve – he doesn’t need to go so far back to hit his backhand."

Corretja then pointed to a few other players he thinks could threaten Rafael Nadal at Roland Garros.

"There are guys out there who can [challenge Nadal]," Corretja added. "There is Novak [Djokovic] of course, there is [Stefanos] Tsitsipas, there is [Alexander] Zverev, there is [Diego] Schwartzman – all whom can play well."

The 47-year-old also threw in the names of Matteo Berrettini and Casper Ruud, but claimed the two are not yet ready to challenge the Mallorcan over five sets.

"Of course we see others like [Matteo] Berrettini, Casper Ruud, these guys can stay with Rafa but I’m just not sure they can over five sets," continued Corretja.

Dominic Thiem & Rafael Nadal cannot face each other before the final at the 2021 French Open

Dominic Thiem and Rafael Nadal at the 2019 French Open

Rafael Nadal is the third seed at this year's French Open, while Dominic Thiem is seeded fourth. This means they will be in opposite halves of the draw and cannot face each other before the final.

The two have met twice in the title round at Roland Garros before (2018 and 2019), with the Spaniard winning both times. But given Thiem's dismal form in recent weeks, it remains to be seen if the World No. 4 can progress to this year's final.