Dominic Thiem is under no illusions as to the colossal task ahead as he prepares for the French Open semi-finals alongside Novak Djokovic, Roger Federer and Rafael Nadal.

For the first time since the 2012 Australian Open, the top four players in the ATP rankings have reached the semis of a Tour-level event, while Djokovic, Federer and Nadal have not all made the last four of a slam since that same year's tournament at Roland Garros.

Thiem, the 2018 runner-up to Nadal, has now reached this stage in four consecutive editions but never before has he faced such a daunting line-up of semi-final foes, the much-vaunted trio boasting 52 major crowns between them.

The Austrian completed a routine 6-2 6-4 6-2 quarter-final success over Karen Khachanov and faces Djokovic on Friday – a man he has beaten twice in eight attempts – before a potential showdown against Federer or 11-time champion Nadal.

"I mean, it's incredibly difficult to win a grand slam," Thiem told a news conference.

"Especially for us players who didn't have one yet, because if everything goes quite normal, we have to beat two players with 15 or more grand slams. So, I think everybody can imagine how difficult this is.

"But I will step on the court tomorrow, try everything, of course, give everything. I hope it's going to be positive in the end, but the challenge is huge.

"Novak is in very good shape again, probably playing his best tennis of his life. I'm in the semi-finals with maybe the three best players of all time, so everybody can see how tough the way it is for me.

"But for me it's amazing. The surface doesn't matter against them. All of them have won all four slams, so surface doesn't really matter.

"They are so tough on any of the surfaces. I think it never happens in any era of men's tennis that you have three players with 15-plus grand slams. I mean, they are the only three with 15-plus grand slams. That shows it all.

"I'm now in the fourth time here in the semis, and I know now how tough it is to get here, to get that deep in a tournament. And these three, they are doing it since, I don't know, 10, 15 years almost at any grand slam. So that shows what their level is. So they are absolutely amazing."