Ex-champion Stan Wawrinka was knocked out of the Australian Open in the fourth round as Canada's Milos Raonic prevailed in a five-set thriller.
The Swiss, who won in 2014, fought back from losing the first two sets before going down 6-4 6-3 5-7 4-6 6-3.
Raonic, 25, hit 24 aces and 82 winners in a match lasting three hours and 44 minutes to reach the last eight.
David Ferrer beat John Isner 6-4 6-4 7-5 and will face Britain's Andy Murray in the quarter-finals.
The eighth-seeded Spaniard, 33, won in straight sets to set up last-eight tie with Murray, who defeated Bernard Tomic 6-4 6-4 7-6 (7-4).
'Peace and quiet'
Thirteenth seed Raonic attributed his performance to inner belief and a "very clear" mental approach.
"That gave me some kind of calm and peace inside," he said. "The more I understand my game, what I need to do, the more I can keep a quiet head on my shoulders."
Meanwhile, French Open champion Wawrinka blamed a lingering cold for his exit, while admitting Raonic was the better player on the day.
"I've been sick for 10 days now," said the 30-year-old.
"I couldn't really be at my best. When you play a top guy like Milos, you need to be 100% to have a chance. He pushed from the beginning and was better."
Novak Djokovic (Serb) v Kei Nishikori (Jpn)
Roger Federer (Swi) v Tomas Berdych (Cze)
Gael Monfils (Fra) v Milos Raonic (Can)
David Ferrer (Spa) v Andy Murray (GB)
Azarenka advances in women's draw
Two-time champion Victoria Azarenka beat Barbora Strycova to set up a quarter-final tie Angelique Kerber.
The Belarusian 14th seed overcame her toughest test of the tournament to beat the Czech 6-2 6-4.
Azarenka, who has never lost to Kerber, had only dropped five games in three matches before facing Strycova.
Kerber moved into the last eight in Melbourne for the first time with a 6-4 6-0 victory over fellow German Annika Beck.
The seventh seed prevailed in a one-hour first set that featured seven breaks of serve, but the 28-year-old raced away with the second.
Kerber, a two-time Grand Slam semi-finalist, will have to be at her best against Azarenka whose brilliant start to this tournament has made her one of the favourites for the title.
Despite admitting to feeling below her best, Azarenka needed just 86 minutes to see off Strycova, who made 33 unforced errors.
"I didn't really feel very good before my match so I'm just happy to win this match, to stay focused and I'm proud of myself for that," said the 2012 and 2013 champion, who has beaten Kerber in their six previous encounters.
Serena Williams (US) v Maria Sharapova (Rus)
Agnieszka Radwanska (Pol) v Carla Suarez Navarro (Spa)
Angelique Kerber (Ger) v Victoria Azarekna (Blr)
Johanna Konta (GB) v Shuai Zhang (Chn)
Murray through to two quarters
In the doubles, Britain's Jamie Murray made it through to two quarter-finals in a day.
He reached the men's last eight in Melbourne for the first time as he and Bruno Soares beat Briton Dominic Inglot and Swede Robert Lindstedt 6-3 6-4.
Murray and new Brazilian partner Soares, who reached the semi-finals in Doha in their first tournament of the year and won in Sydney, will play 13th seeds Raven Klaasen and Rajeev Ram after they beat American twins Bob and Mike Bryan 3-6 6-3 6-4.
The Scot and mixed doubles partner Katarina Srebotnik then progressed to the last eight thanks to a 6-4 6-4 win over Anna-Lena Groenefeld and Robert Farah.
'I'm lucky not to have a fracture'
Gael Monfils overcame Andrey Kuznetsov 7-5 3-6 6-3 7-6 (7-4) to set up a quarter-final against Raonic.
The Frenchman is renowned for his court coverage but admitted he was fortunate not to suffer a more serious injury after one spectacular dive during his victory.
"It's very painful," said the Frenchman of his unsuccessful attempt at a full-length retrieve. "I cannot even grip anything right now and I have a deep cut. That's nothing. I have a bruise but I'm lucky not to have a fracture.
"During the point, I feel that I can [reach] it. So I just do it because I think I have the ability to do it. But you know, I'm not a rock."