In a recent interview, Dominic Thiem commented on who can be a threat for Rafael Nadal on clay. The Austrian player said: "As long as Rafa plays, he will always be the ultimate favourite in any clay tournament, but now there are bigger challenges for him than in the last years.
Zverev is always a threat, Djokovic is at his best again. And there are younger players like Auger-Aliassime, Stefanos Tsitsipas or Denis Shapovalov. There are a lot of challenges for Rafa. Comparing myself to Felix, Tsitsipas or Shapovalov, I was very bad at 18 years of age and they are already very good, they are on the top 10, top 20, top 30.
When I was 18 years old, I was like world No. 700. Recalling how I played I am shocked because I was much worse than them. When I joined the top 100, I was the second youngest player there. The situation has changed, it's a normal evolution of tennis, there are very strong young guys and in the next four years there are 10-15 players who can get to the top of the rankings.
I think they are unbelievable because they play great tennis. When I was as old as them, I think only me and Jiri Vesely were there and now there are 15 very young guys on the top 100, including someone like Zverev and Tsitsipas on the top 10.
I cannot choose who is the best out of them because everyone plays very well and they have chances to win Grand Slams and be No. 1 one day."