Dominic Thiem is braced for the "toughest match you can imagine" against Rafael Nadal in the semi-finals of the French Open after ending Novak Djokovic's reign on Wednesday.

Thiem was beaten by Djokovic in his only other run to the last four of a grand slam last year and was hammered by him in Rome last month, but gained revenge with a 7-6 (7-5) 6-3 6-0 victory on Court Suzanne Lenglen 12 months later.

The sixth seed from Austria had never beaten the defending champion in five attempts, but put that right to ensure he will face tournament favourite Nadal on Friday.

Thiem is the only player to beat the history-chasing Spaniard on clay this year, in the Italian capital before losing to Djokovic, but knows he will need to produce something special to repeat that feat in Paris.

"First of all, it's great for me to be in the semi-finals again." said the 23-year-old. "And of course, I think on Friday I am facing the toughest opponent ever here in Roland Garros.

"It's going to be the fourth match against him in, like, five or six weeks. There will not really be big secrets, he's in his best again shape. So it's going to be the toughest match what you can imagine."

Reflecting on his maiden victory over Djokovic, Thiem said he felt the first set was crucial and sensed the Serbian was there for the taking after clinching the opener on a tie-break.

He said: "The first set was very, very long and very close. Then in the second set, in the beginning, I was down love-30. I still made the game and broke him in the first service game and again broke him in his first service game in the third set.

"That's very tough. It's understandable that there is a little bit of tough things mentally coming up to him. And that's why at the end it was probably a little bit easier."