MELBOURNE — So much for the thought that Rafael Nadal's bad back might hold him back at the Australian Open as he tries to break a tie with Roger Federer for the most Grand Slam singles titles won by a man.
Win three more matches this week, and Nadal will be the only one with 21.
So far, he hasn't dropped a set through four matches, moving into his 13th quarterfinal at Melbourne Park and 43rd in all at major championships with a 6-3, 6-4, 6-2 victory over No. 16 seed Fabio Fognini on Monday.
Take it further, to the start of last year's French Open, and Nadal has won his past 33 Grand Slam sets in a row.
He called the first set against Fognini "without a doubt" his "best level in the tournament."
Why was that? Well, the 34-year-old Nadal offered a rather simple explanation: He came into the match finally having been able to practice for two days in a row, after having his work limited by the back pain that surfaced about three weeks ago.
Not that everything is perfect, mind you.
"My physical condition needs to keep improving," Nadal said. "But I think this match helps, too. I was not able to practice the proper way for the last 19 days, but yesterday I started again to increase the amount of work (in) practice. And today has been a positive victory with some long points, so that helps for the next match."
That'll be on Wednesday against No. 5 seed Stefanos Tsitsipas, who advanced when his fourth-round opponent, No. 9 Matteo Berrettini, pulled out of the tournament because of abdominal injury he picked up in his prior win.
Before Berrettini's withdrawal officially was announced, Nadal accidentally broke the news by telling the media he'd be facing Tsitsipas.
Nadal is 6-1 against the 22-year-old Tsitsipas, including a 6-2, 6-4, 6-0 win for the Spaniard in the 2019 Australian Open semifinals.
The other quarterfinal on their half of the draw will be No. 4 Daniil Medvedev, the 2019 U.S. Open runner-up, against No. 7 Andrey Rublev in an all-Russian matchup between friends since childhood.
"Of course he knows my game. I know his game," said Rublev, who has lost all three tour-level meetings with Medvedev. "But in the end, you still need to … see how the things are working or not working, how you're feeling, and then you adapt."
Serena Williams is performing a delicate balancing act at the Australian Open as she pursues a record-tying 24th major title.
Her coach, Patrick Mouratoglou, says Williams needs to think about what is in the offing — but not too much.
"The only way is not to think about the opportunities. Because when you think about the opportunities, you bring expectations, and we all know that expectations are not the best friend of the professional athletes," Mouratoglou said. "The only way is to focus on how to get what you want. You don't think about what you want. You just think about what you have to do."
Williams faces No. 2 Simona Halep in the quarterfinals on Tuesday. The last time they played, in the 2019 Wimbledon final, Halep made just three unforced errors in a 6-2, 6-2 victory.
That part of a stretch in which Williams has gone 0-4 in Grand Slam title matches since claiming her most recent major singles trophy at the Australian Open in 2017 for No. 23, a record for the professional era.
Only Margaret Court, with 24 spanning the amateur and Open eras, has won more.
Paul McNamee, the former player and ex-CEO of the Australian Open, is now coaching quarterfinalist Hsieh Su-wei and recalls seeing her unusual, but precise, strokes go awry one day at a tournament in England.
He couldn't figure out what was going on — until he realized she had broken a racket string, something that almost never happens to her.
"We had a bit of trauma because she had to get a re-string before the tournament. That's once a year," he said. "Players change rackets on the change of balls, right? She'll go years with the same racket."
McNamee said Taiwan's Hsieh, who is ranked 71st and faces Naomi Osaka on Tuesday at Melbourne Park, doesn't have a racket contract. So she has to buy her own.
Whatever 35-year-old Hsieh has been doing at the Australian Open, she should stick with it. She is the oldest woman in the professional era to get to a Grand Slam quarterfinal for the first time.