Milos Raonic was just overwhelming Alexander Zverev with consistency, compounding the frustration with every service break.

Roanic dropped serve in the opening game of their fourth-round match at the Australian Open but then went on a roll, winning eight straight games before fourth-seeded Zverev held serve.

No let up. Raonic held and then broke the 21-year-old German player's serve again to lead 4-1 and that's when Zverev lost it.

At the change of ends he destroyed his racket by smacking it into the court eight times, then tossing it away.

The angry outburst only served to highlight Raonic's dominance.

"I played incredible today," the 2016 Wimbledon runner-up said. "I did a lot of things very well. Proud of that."

And so he should be. He's into the Australian Open quarter-finals for the fourth time. And he's achieved that from a tough part of the draw.

WATCH | Milos Raonic disposes of Alexander Zverev :

Milos Raonic ran over Alexander Zverev in surprising fashion 6-1, 6-1, 7(7)-6(5) to move on to the Aussie Open quarter-finals. 1:54

He opened with a win over the enigmatic Nick Kyrgios, who had all the home-won support, and followed that up by coming back to beat three-time major winner Stan Wawrinka in four tiebreak sets. The 16th-seeded Raonic then beat Pierre-Hugues Herbert in three tiebreakers.

At 28, Raonic feels like he's on the verge of being back as a contender at the majors. Zverev, an undoubted talent, is yet to beat a top 20 player at a Grand Slam.

Raonic was so consistent with his serve — 15 aces, one double-fault, 16 of 19 first serves into play for the second set — and kept his unforced error count down to 24 for the match. He said he could sense his rival's growing rage.

"It was pretty clear what was going on," he said. "It can have an effect a lot of different ways. You know, if you're a top guy and you do that against somebody who doesn't have experience, it might sort of cause them to retreat a little bit.

"I have sort of faced that situation, and I was also ahead at that point, so I was just really focusing on myself."

Zverev got the inevitable warning for racket abuse, took a break at the end of the second set and returned from the locker room a much calmer, more composed player.

"Yeah, it made me feel better," Zverev said. "I was very angry, so I let my anger out."

Zverev lost only one point in his first four service games in the third set, but then Raonic stepped up the pressure again.

"I played bad. The first two sets especially I played horrible," Zverev said. "I mean, it's just tough to name one thing. I didn't serve well, didn't play well from the baseline. Against a quality player like him, it's tough to come back from that."

Zverev saved two match points in the 10th game of the third — one with a short slice backhand that Roanic ran for but couldn't retrieve to end a 29-shot rally and another that clipped the baseline.

But Raonic rallied from 3-1 down in the tiebreaker and finally converted on his fourth match point. He'll next play either No. 11 Borna Coric or No. 28 Lucas Pouille in the quarter-finals.

Zverev smashed his racket in frustration during a break while playing against Raonic at the Australian Open. (Paul Crock/AFP/Getty Images)

Djokovic overcomes 2nd-set struggles

Top-seeded Novak Djokovic overcame a couple of tumbles to the court and a series of energy-sapping baseline exchanges — one point lasted 42 strokes — to get back to the Australian Open quarter-finals for the first time since 2016 by beating No. 15 Daniil Medvedev 6-4, 6-7 (5), 6-2, 6-3.

Djokovic has won six of his 14 Grand Slam titles at Melbourne Park and is into his 10th quarter-final at the hard-court tournament.

WATCH | Djokovic defeats Medvedev:

Top-seeded Novak Djokovic beats Daniil Medvedev in 4 sets. 0:30

He is feeling sore and tired but thinks he will be OK for his Australian Open quarter-final match against Kei Nishikori.

"I didn't feel so great, you know, in the last 20 minutes of the match or so," Djokovic, aiming for a record seventh men's title in Australia. Immediately after the match, he said in a TV interview that he had never felt fresher.

Djokovic exited in the fourth round last year and the second round in 2017.

After edging Medvedev in a three-hour 15-minute struggle, Djokovic joked during an on-court interview: "Since I guess my next opponent is watching, I'm feeling fantastic. I've never felt fresher in my life."

Nishikori, whose own fourth-rounder was even more grueling, going to a fifth-set tiebreaker and lasting five hours five minutes.

Williams outlasts Halep

Serena Williams faced her first real test at this year's Australian Open and emerged with a 6-1, 4-6, 6-4 victory over No. 1-ranked Simona Halep to reach the quarter-finals.

It was a back-and-forth match filled with momentum swings and terrific play by both.

WATCH | Williams defeats Halep:

Serena Williams defeats Simona Halep 6-1, 4-6, 6-4 to reach the quarter-finals. 1:22

"It was a really intense match, and it was some incredible points," said Williams, who improved to 9-1 against Halep and now meets 2016 U.S. Open runner-up Karolina Pliskova in the quarter-finals.

The 37-year-old American sat out last year's Australian Open after giving birth to a daughter months earlier and dealing with health complications. Since returning to the tour, Williams has reached the past two Grand Slam finals, losing both — and leaving her still one shy of equaling Margaret Court's record of 24 major singles titles.

Williams gained control for good after saving three break points in a monumental game to hold for 3-all in the third set. She then broke for a 4-3 lead and finally was on her way.

Williams is trying to win an eighth championship at Melbourne Park.

Osaka draws Svitolina

U.S. Open champion Naomi Osaka is into her second Grand Slam quarter-final after another comeback win, this time over Anastasija Sevastova.

Osaka had to work for nearly two hours on Rod Laver Arena to subdue the gritty Sevastova 4-6, 6-3, 6-4 in a fourth-round match studded by service breaks.

She'll next play sixth-seeded Elina Svitolina, who had a 6-2, 1-6, 6-1 win over 2017 U.S. Open finalist Madison Keys. Osaka won a tight three-setter when she met Sevastova at the Brisbane International in the first week of the season.

Naomi Osaka will face Elina Svitolina in the Australian Open quarter-finals. (Peter Parks/AFP/Getty Images)

Sevastova grabbed the lead in the opening set on Monday, and clinched it with a deft drop shot that forced Osaka to fly a forehand over the baseline. Osaka had to stave off two break points in the third game of the second to edge ahead.

The fourth-seeded Osaka grew in confidence from the narrow escape and lifted her tempo and shot-making consistency, grabbing the crucial service break in the sixth game.

Serving to level the match, Osaka fended off a break-back point with a brilliant forehand volley after a long, tense baseline rally. Two points later, the match was heading into the deciding set. Osaka broke serve to open third set to maintain the momentum.