EXCLUSIVE: 'Remarkable' Jannik Sinner trait exposed by doping saga

Jannik Sinner will walk out onto Rod Laver Arena on Sunday night for the Australian Open final against Alexander Zverev with a potential year-long doping ban hanging over his head.

The Italian world No.1 will front the Court of Arbitration for Sport on April 16-17 after the World Anti-Doping Agency appealed the court's decision not to enforce a ban.

Sinner twice last year tested positive to Clostebol, a banned anabolic steroid. International Tennis Integrity Agency determined his physiotherapist had used a spray that contained the drug.

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Reports suggest Sinner could be banned for anywhere between one month and one year.

Speaking on Wide World of Sports' The Morning Serve, Jim Courier said having that cloud hanging over his head makes Sinner's performance this month all the more "remarkable".

"I'm sure that's been in his mind, but he's been able to put that to the side and find a way to play his best tennis," he said.

Sinner is on a winning streak dating back to last October. He's dropped only two sets on his run to the final.

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But questions linger over his fitness heading into Sunday night's decider. In his fourth round match against Holger Rune, he was visually trembling as he battled an undisclosed illness.

While there were no signs of that illness in his straight-sets demolition of Alex de Minaur two days later, he required treatment for cramping and was in visible discomfort at stages of his semi final against Ben Shelton.

But down the other end, Zverev, too, has dropped only two sets. Crucially, he also played only one set - albeit a very long one - in his final against Novak Djokovic.

It all means Sinner, having looked untouchable for months, could be vulnerable.

"Only Jannik knows what he's actually feeling," Courier continued.

"Sometimes those cramps can come from nerves, sometimes they come on from physical exertion. He was having the pickle juice the other night which may indicate it was fatigue.

"He will want to play faster points. That's his MO - he likes to play offence off the forehand and the backhand side.

"But Zverev is one of the best shock absorbers and point-extenders we've seen in men's tennis. He's rangey, he's fast for his size, and he is so determined to stay in those rallies.

"This could be the wrong match up for Sinner if he's not feeling great."