And he thinks his next opponent Alexei Popyrin will present an even bigger obstacle.

“I really did not believe that Novak was going to have such a huge test today. But credit to his opponent Jacob, who really fought until the end: never gave in, never gave up.

“But on the other hand, you could see that Novak is not moving as crisply as he usually does. And maybe that’s where you could tell that there was a three-week break after Roland-Garros.

I think the first real, real test is going to be the Popyrin match

“And of course, if he wants to go to the later stages of this tournament, he is going to have to raise his level tennis-wise and physically-wise as well. So on one hand, it’s a good sign that he played for three hours and that there wasn’t any pain in the knee. But if he wants to progress and if he wants to challenge for that title, he can’t afford – I think at this point in time – to play a long matches in the early rounds.

“Next comes Popyrin, who had, I think, four set points to go 2-1 up at the Australian Open. So he can obviously take some belief and confidence from that match. And now he’s going to have to turn up, you know, really, really turn up, to have his first serve percentage really up.

“Of course it’s going to be a different sort of match. I think Novak needs to be on top of his returns. He usually reads Popyrin’s serve really well. But I’m a bit ambivalent about this match for Novak, because I really think that he could have used another quick match. And that’s why most of his fans were happy with the draw in the first two rounds, because they thought it would give him time to adapt, to raise his level, to feel more confident.

“But this was an unexpected test. There is a lot of room to improve in every aspect of the game, tennis-wise and physically. And I think Novak is very aware of that. Of course, it was windy today. It was windy for both players, but we know that Novak struggles maybe more with the windy conditions than some other colleagues of his.

“So yeah, let’s see. I think the first real, real test is going to be the Popyrin match.”