If not for Thanasi Kokkinakis, Greek showman Stefanos Tsitsipas would barely have raised a sweat on the way to his Australian Open quarter-final showdown with history-chasing Rafael Nadal.
The No.5 seed dropped a total of just 10 games in his first and third-round wins over Gilles Simon and Mikael Ymer.
And he didn't even get to set foot on Rod Laver Arena on Monday night after his fourth-round opponent and No.9 seed Matteo Berrettini withdrew with an abdominal strain.
So if Nadal is looking for any recent pointers on how best to stretch Tsitsipas he would be well advised to study the second-round clash at Melbourne Park where Kokkinakis was just shaded in a five-set thriller stretching over four and a half hours.
The Spanish world No.2 pulled out of the ATP Cup earlier this month with a back injury.
Nadal's form and fitness have both improved as the Open has progressed, and he rated the opening set of his fourth-round win over Italian Fabio Fognini as the best tennis he has played this year.
"That's normal because I was able to practise for two days in a row," said Nadal.
"That makes an important difference.
"But at the same time it's important to find positive feelings now.
"My physical condition needs to keep improving but I think this match (against Fognini) helps, too.
"I was not able to practise the proper way for the last 19 days, but yesterday I started again to increase the amount of work on the practice court and today has been a positive victory with some long points."
Despite initial concerns about his troublesome back, Nadal has advanced to the last eight without dropping a set as he chases a record 21st major title, which would move him one clear of Roger Federer.
He was beaten at the same stage last year by eventual finalist Dominic Thiem.
"It was a good match and I had my chances," said the 34-year-old Spaniard, whose only Australian Open title came back in 2009.
"I remember I served for the set in the first set and then lost a couple of tiebreaks."
Finding a way to break the Tsitsipas serve will be crucial for Nadal if he is to triumph on Wednesday.
The powerhouse Greek has faced just four break points to date in this tournament and only dropped serve only once in 48 games.
That's the best serving record at the 2021 Open.