Comesana belied his lack of experience, playing with poise and control from the start. The 23-year-old broke his opponent for a 3-2 lead in the first set and then held to win it, much to the frustration of Rublev, who frequently screamed out loud and remonstrated with his courtside coaching team.

Rublev broke early in the second and began to assert himself, frequently wrong-footing Comesana or drawing him into long rallies and overpowering him with powerful forehand shots.

Comesana fought his way back from three set points down twice in the second set before losing it.

But the Argentinian, who fired down 21 aces in all, powered through the rain-interrupted third set and narrowly outdid Rublev for guile and accuracy in the fourth before drawing an unforced error from the Russian to finish the match in style. 

At one point in the third set the 26-year-old, who also had a meltdown at the French Open in May, smashed his racket repeatedly over his knee, leaving it bloody and bruised for the rest of the match.

"I didn't behave today as in Paris, but still I could do much better. This is not the way. Of course it's the main priority to be able during all the match to be positive," he told reporters, while acknowledging his opponent's fine performance.

"I had a lot of chances, a lot of opportunities. I didn't make them. The guy was playing really well, 10-points mentality, and he deserve to win," he said.