Denis Shapovalov is knocking on the door again. What are his chances of repeating his performance against Zverev in the quarters, against Rafa?

INTERVIEW: Denis Shapovalov after his fourth-round win over Alexander Zverev

“It’s never over with Shapo,” the Australian commentator said midway through Denis Shapovalov’s 6-3, 7-6 (5), 6-3 win over Alexander Zverev on Sunday.

Normally, when we use that phrase to describe a top-level tennis player, we mean that he or she is never out of a match, and always fights to the end. In this case, the meaning was the opposite: The commentator was trying to say that whoever is playing Shapovalov is never out of it, even when he’s behind in the score, because the Canadian can find a way to keep him in it.

It was a tough statement to make about someone ranked 14th in the world, but it’s not inaccurate. For all of Shapovalov’s talents, and for all of the improvements he’s made during his time on tour, he’s still prone to sudden spates of mistakes. And he was hardly flawless against Zverev: Shapovalov double-faulted 11 times and made more errors (37) than winners (35).

Yet he also came away with one of the best wins of his career, and pulled off one of the surprises of the season so far. Before the tournament began, Zverev described himself, along with Novak Djokovic and Daniil Medvedev, as part of “the new Big Three.” That was obviously a stretch, but at the time, the Serb, the Russian and the German seemed to be the clear favorites to win the men’s title at the Australian Open. Since Wimbledon, breaking through Zverev’s defenses, and breaking his serve, have become two of the toughest tasks in tennis.

I wrote before the match that Shapovalov had a “slasher’s chance.” He has the lethal, if erratic, attack that can put anyone, including Zverev, on his heels. Shapovalov took that chance in this match. He didn’t hesitate to aim for the corners or dash forward whenever possible. He hit twice as many winners as Zverev (35 to 18) and was 22 of 27 at net.

Most important, Shapovalov didn’t let a couple of bad games in the second set turn into a lot of bad games. When he was broken, he broke back; and he built such a big lead in the second-set tiebreaker that even a few wobbles down the stretch didn’t cost him.

“Just think I played smart,” said Shapovalov, who moved back on his return to give himself a longer look at Zverev’s powerful serve. “Felt pretty comfortable from the back. Felt like I was outplaying Sascha on the baseline.”

The opposite was true for Zverev. Asked what went wrong, he said, “Everything.” He looked uncomfortable in the heat, he looked tentative and out of rhythm on his serve and forehand, and he squandered every chance he had to get back in the match.

“There’s not much I can say or take away that was positive from today,” Zverev said. “Maybe since Wimbledon, one of the worst matches I’ve played. Obviously I give credit to Denis….[But] today was just awful from my side.”

“I came here with a goal to win, and maybe to become No. 1 and all that. But if I play like that, I don’t deserve it. It’s as simple as that.”

Maybe since Wimbledon, one of the worst matches I’ve played. Obviously I give credit to Denis….[But] today was just awful from my side. Alexander Zverev

Shapovalov, still sneaky young at 22, is into his third Grand Slam quarterfinal, and his second in his last three majors. The last time he went this far, at Wimbledon, he lost in three close and exciting sets to Novak Djokovic in the semifinals, and left Centre Court in tears. Shapovalov said he was disappointed because it was the first time he had actually believed he could win a Slam, and then, when the opportunity arrived, he couldn’t make it happen.

Now he’s back knocking at the door; to get through it, he’ll have to beat an equally formidable opponent, Rafael Nadal. Does he have a better chance? Having played Djokovic in a Wimbledon semifinal should help. Having an experienced new coach, Jamie Delgado, in his corner, should help. And so should his success against Zverev. Finding a balance between aggression and patience is key to beating the German and the Spaniard.

“It’s definitely something I've been learning to do,” Shapovalov said of staying patient. “Hasn't come natural to me, unfortunately. I’ve always wanted to, you know, to play quick and go for my shots.

“But it’s difficult when you play a guy with the caliber like Sascha. You know, you can’t go through him in one or two shots. You have to stay in the rallies, you have to work for the points. Then when you have an opportunity then you can swing in and go for it.”

Shapovalov will have to keep those words in mind against Nadal. He famously beat him in Montreal in 2017, and he nearly beat him on clay in Rome last year. So he’ll have a slasher’s chance again. But so will Rafa.