Novak Djokovic

MELBOURNE, Australia — Novak Djokovic sought assistance from a trainer for some trouble breathing Friday night, and went back-and-forth with one particularly loud spectator, but when the ball was in play at the Australian Open against Tomas Machac, all went quite smoothly for the 24-time Grand Slam champion.

Djokovic, a 10-time title winner at Melbourne Park, moved into the fourth round with his most confident performance of the week, a 6-1, 6-4, 6-4 victory over the 26th-seeded Machac — who actually won their most recent previous encounter, last season.

Asked in a post-match interview how he thought things went, Djokovic replied: “Very hot-headed right now, so I’m going to try to give a calm and diplomatic answer to that. I think I played really well. I’m very happy with my game. I was surprised, to be honest, with the result.”

It all lasted less than 2 1/2 hours, and Djokovic was broken only once and converted 5 of 15 chances on Machac’s serve. One other barometer of how well it went: Djokovic amassed 28 winners to just 20 unforced errors.

It was his first straight-set victory this year in Melbourne, after getting pushed to four in the first round by 19-year-old Ninesh Basavareddy and in the second by 21-year-old Jaime Faria. Both of those opponents were making their Grand Slam debut.

He’ll face No. 24 Jiri Lehecka on Sunday, with the winner possibly taking on No. 3 Carlos Alcaraz in the quarterfinals.

At the end of the initial game of the second set in Rod Laver Arena, Djokovic looked uncomfortable and grabbed at the right side of his rib cage. Then, at the ensuing change of ends, he took the unusual step of taking a seat on his sideline bench instead of just walking around the net to the opposite baseline.

In the very next game, Djokovic missed a drop shot to make it 15-40, and he leaned forward, chest heaving, and put his hands on his knees. Machac then converted the first break chance for a 2-0 lead in that set when Djokovic missed a difficult volley.

But Djokovic broke right back, eliciting chants of his nickname, “Nole!” from the stands and getting his coach, Andy Murray, to stand and applaud in his courtside box.

Djokovic then asked the chair umpire to call for a trainer. Djokovic sat down for the changeover and draped a white towel over his head, before he received some medical attention.

“I was trying to catch my breath. I struggled. I’m not 19 anymore — I’m 19 times two, almost,” joked Djokovic, who turns 38 in May.

And although he acknowledged that he “struggled physically” in the middle of the match, by the final set, Djokovic said, he “felt fresh; moved really well.”

Later on, he was bothered by someone yelling from the stands during points. As the end neared, Djokovic flexed and screamed after winning a point. When Djokovic finished off the win, he pointed to his ear, as though to say, “Well, what do you have to say now?”

When a voice called out during Djokovic’s interview, he responded, “Sorry, mate. I have a wife. We can have a drink, though,” then added: “Maybe you had a few already.”

“I’m happy to have a drink with him, now that the match is over,” Djokovic said. “I think we can reflect nicely on what we have said to each other.”