MELBOURNE, Australia — After missing the game he has long played with such passion, Rafael Nadal has had ample opportunity to get reacquainted with tennis at this Australian Open.

At age 35, his latest comeback from injury now finds him in the semifinals, just two victories from breaking his three-way tie with Novak Djokovic and Roger Federer and claiming his 21st Grand Slam singles title.

But it also briefly found him on the defensive Tuesday after his opponent, Canada’s Denis Shapovalov, said Nadal had benefited from favoritism in their quarterfinal, which Nadal won by taking command of the fifth set to prevail, 6-3, 6-4, 4-6, 3-6, 6-3, in four hours and eight minutes.

Nadal politely rejected the accusations by Shapovalov, a young Canadian. “I think he is wrong,” Nadal said.

Shapovalov, who certainly did not help his cause by playing an edgy, error-filled game to drop his serve early in the fifth set, did not take the defeat well, smashing his racket to the blue hardcourt in Rod Laver Arena immediately after his final volley drifted wide. It was a stark contrast with Nadal, who has never broken a racket in anger during a match in his nearly 20-year professional career.

But Shapovalov was both crestfallen and disappointed with Nadal, the Spanish champion whom Shapovalov first met as a nine-year-old ball boy during the Canadian Open in Montreal and then defeated, Hollywood-style, in the same city in their first match in 2017.

However wide-eyed Shapovalov might once have been about the Spaniard, he did not hold back on Tuesday: complaining during and after the match that Nadal was being allowed more time between points than permitted.

After winning the first set, Nadal changed his clothes and was slow to leave his chair after the umpire, Carlos Bernardes, called “Time.” Shapovalov took the balls and prepared to serve as he waited, and when Nadal finally made it on court about 45 seconds after Bernardes’s announcement, Shapovalov approached Bernardes and said Nadal should have been penalized for the delay.

Bernardes did not agree, and Shapovalov returned to the baseline and then approached Bernardes again, saying Nadal still was not ready. Bernardes answered: “You’re not ready to play either because you come talk to me.”

“Are you kidding me?” Shapovalov said as he retreated. “You guys are all corrupt.”

Shapovalov, 22, received no code violation for the comment, although he could be fined or sanctioned by the Australian Open after further inquiry. Shapovalov later said, apologetically, “I think I misspoke.” He was involved in another exchange with Bernardes as Nadal prepared to serve the second game of the second set even though there were still several seconds on the serve clock. Nadal came toward the net. Shapovalov met him there and after a brief exchange play resumed.

“It was nothing against Rafa,” Shapovalov said. “Rafa was serving, and I would expect the umpire to be looking at Rafa, and the umpire was staring me down. It didn’t make sense to me.”

But Shapovalov was not done complaining about Nadal, arguing with Bernardes after the fourth set that Nadal, who had been examined briefly on court for stomach problems, was stretching the spirit of the rules by taking an extended break off court before the final set for a combined medical evaluation and toilet visit.

Nadal explained later that he began feeling poorly late in the second set, most likely because of the hot, humid weather and his long break from the game. He returned to the tour this year after missing five months with a chronic foot problem and then contracted Covid-19 in late December at an exhibition in Abu Dhabi. He is seeded sixth in Melbourne, where he won the title in 2009.

Shapovalov quizzed Bernardes at length as they awaited Nadal’s return, saying that he had not been allowed to combine the two breaks at a past tournament. Nadal served seven minutes after the fourth set had been completed.

Asked at a post-match news conference if Nadal received preferential treatment, Shapovalov answered “100 percent he does” and said there needed to be boundaries.

“Every other match that I have played, the pace has been so quick because the refs have been on the clock after every single point,” Shapovalov said. “This one, I mean, after the first two sets it was like an hour and a half just because he’s dragged out so much after every single point. He’s given so much time in between sets and all this.”

Players are allowed 25 seconds between points when serving but chair umpires have discretion on when to start the shot clock. When returning serve, players are expected to play to the server’s “reasonable pace,” a phrase in the tennis rule book that leaves plenty of room for interpretation.

“I respect everything that Rafa has done and I think he’s an unbelievable player,” Shapovalov said. “But there’s got to be some boundaries, some rules set. It’s just so frustrating as a player. You feel like you’re not just playing against the player; you’re playing against the umpires, you’re playing against so much more. It’s difficult. I mean, it was a big break after the fourth set and for this reason the momentum just goes away.”

“They are legends of the game,” Shapovalov said of stars like Nadal, “but when you step on the court it should be equal.”

Bernardes, a veteran chair umpire from Brazil, did give Nadal a time violation for taking too long before serving in the fourth set. Bernardes and Nadal have not always been in agreement, and Bernardes was kept from working Nadal’s matches during a cooling-off period in 2015. But that informal ban soon ended.

Nadal rejected Shapovalov’s accusations of favoritism and said it was standard practice to take a bit more time to change clothes and equipment after a set played in such steamy conditions.

“I think he really was wrong,” Nadal said in Spanish of Shapovalov. “When you lose a match like this, you are frustrated. I have a lot of affection for Denis. I think he’s a good guy with lots of talent, the talent to win multiple Grand Slams. In no way do I want to get in an argument with him. But I think he’s wrong. He’s young and when one is young, one makes mistakes.”

Nadal observed that the rules had been tightened in recent seasons to make it harder to show favoritism to the elite or any player because of the advent of electronic line-calling, shot clocks between points and, this season, stricter time limits on toilet breaks.

“You have less room now to influence anything,” said Nadal, who added that he was not interested in getting an advantage on court.

“I really believe that on the court you don’t deserve better treatment than the others,” Nadal said. “And I really don’t want it, and I don’t feel I have it.”

Nadal was often far from his best in the second half of Tuesday’s match: missing some of his familiar forehand passing shots on the run by large margins. He also had 11 double faults, a large amount by his standards. But he was able to serve well when he needed it most, including coming up with an ace to save a break point in the opening game of the fifth set and saving two more break points in the third game.

“I was destroyed honestly, physically, but my serve worked well,” Nadal said. “For me, every game that I was winning with my serve was a victory.”

He got the overall victory, too, and will now have two full days to recover before facing No. 7 seed Matteo Berrettini or No. 17 seed Gaël Monfils in the semifinals on Friday afternoon. Nadal usually prefers to play in the daytime, where conditions are typically quicker and help his topspin forehand penetrate the court. But he looked as if he would have been delighted to play in the shade against Shapovalov.

“I’m not 21 anymore,” Nadal said wearily in his post-match interview on court.

But 21 could still be his magic number in Melbourne, where he is just two matches away from breaking a tie.