John McEnroe thought Alexander Zverev looked 'flat as a pancake' in his Australian Open final defeat against Jannik Sinner.

Sinner only dropped two sets over the course of the year's first Grand Slam tournament but sickness and injury issues forced him to dig deep. The Italian suffered dizziness and was seen shaking during his fourth-round win over Holger Rune.

Cramps and spasms then struck against Ben Shelton in the semi-finals. But McEnroe believes that Zverev looked more like the player in physical distress on Sunday, as he was unable to put Sinner under any real pressure despite the 23-year-old's rocky road to the final in Melbourne.

"I thought he’d try and get into a war of attrition," McEnroe told Eurosport. "Try and test Sinner, who cramped two days ago and got sick four days ago. He wasn’t able to do that, but you have to give credit to Jannik, who took him right out of the match."

Sinner ultimately cruised to victory Down Under, with a second-set tiebreak the only glimpse Zverev had of getting on the board as the match finished 6-3 7-6 6-3.

"I was really surprised at the level Zverev came up with at the end of the second set and the third set," McEnroe continued. "I don’t know what happened to him.

"He had no energy, he was flat as a pancake. He looked like the guy who got sick a couple of days ago, he looked weary and he played one set in five days. I don’t know what happened."

Zverev has now reached three Grand Slam finals without getting over the line. And seven-time major winner Mats Wilander has concerns about whether the German has the mental fortitude to break his duck.

"I'm starting to wonder if there is the self-belief," he told Eurosport.

"When I see his performance [against Sinner], not in terms of how he hit the ball or tactics, but in terms of emotional input, I’m starting to wonder if… I’m sure he believes early in the match, but you have to believe in the third set, when you win the first point in the last game.

"You have to bluff your opponent and when he doesn’t do that, it worries me, to be honest."

Having won the Australian Open title for a second consecutive year, Sinner has consolidated his spot at the top of the men's rankings, with Zverev suring up second place.