Courier thinks Sinner was in a testing phase: "He's trying to get to a higher level to prepare for the big games".

Jannik Sinner's Round of 16 match on Monday could be a tight affair against Holger Rune, a player against whom previous duels have been tight (2-2 in the history of confrontations).

Not necessarily at his best in his first three matches at this Australian Open, the world No.1 dropped a set against Australian guest Tristan Schoolkate in the 2nd round, and committed 37 unforced errors against Marcos Giron in the 3rd round.

Although his average level is sufficient to get by, Sinner will face his first test in Melbourne against Rune.

But according to Eurosport consultant Jim Courier, Sinner was simply working on other aspects of his game for the most important matches of the tournament:

"He knows that his base level allows him to win matches like this. He also knows that his bad days are better than anyone else's, including Carlos Alcaraz.

But I think he understands that his best day against Alcaraz's best day is not in his favor.

Alcaraz always has extra speed because he has so many different options.

For me, Sinner is trying to get to a higher level, which means more options in his game, because he needs to prepare for the big games."