Novak Djokovic survived an almighty fright from Frenchman Gilles Simon, as the defending champion struggled to a 6-3, 6-7 (1-6), 6-4, 4-6, 6-3 win for a place in the quarter-finals of the Australian Open on Sunday.
Djokovic, who committed an unprecedented century of unforced errors, only escaped after more than four and a half hours of battle.
A 21-minute opening set meanwhile set the tone for Roger Federer's 6-2, 6-1, 6-4 post-midnight crushing of Belgian David Goffin..
The Swiss third seed takes a 15-6 record into his next match - and 47th grand slam quarter - with Tomas Berdych, who beat Spaniard Roberto Bautista Agut 4-6, 6-4, 6-3, 1-6, 6-3.
Federer posted his 79th win at Melbourne Park with a dominating command performance as he beat Goffin for a fourth time.
"I'm very very happy that I came out and played as well as I did," Federer said. "I couldn't be happier. It was a nice surprise out here tonight for me."
Simon, the 14th seed, saved two match points in the eight game of the fifth set after trailing 5-1 on a double-break. The French player recovered to 5-3 before Djokovic closed it out a game later, sending a backhand winner down the line on his third match point.
The struggle sent the world number one into a 27th consecutive grand slam quarter-final, tying him on joint second with Jimmy Connors.
The Serb will next face Kei Nishikori after the Japanese seventh seed beat Jo-Wilfried Tsonga 6-4, 6-2, 6-4. Djokovic leads that series 5-2.
Djokovic was quick to admit he almost didn't get the job done on court.
"Playing someone like Gilles, can expect lot of rallies. He always makes you play the extra shot," he said.
"He knows how to play, we had a great match and a great fight. He is one of the best counter-punchers and has beaten big players on the big stage. He's not overwhelmed by the occasion.
"I had a lot of unforced errors, he was fighting and playing well. Physically it was a very demanding match and I'm very glad to get through this one.
"I hope to decrease by unforced error statistic in the next round and perform my best."
Djokovic has now defeated Simon in 10 of 11 meetings. He was taken to five sets for the first time since Wimbledon in July against Kevin Anderson.
On the women's side, Maria Sharapova and Serena Williams will meet for the 21st time after the two multiple grand slam champions dispatched up-and-coming players in the fourth round.
Five-time grand slam winner Sharapova had to work to school Swiss teen Belinda Bencic 7-5, 7-5 while Williams started by losing serve but was then untroubled as she beat Russian Margarita Gasparyan 6-2, 6-1.
Williams has defeated Sharapova in 18 of 20 meetings, including the 2015 Melbourne final.
"You're always trying to improve," Sharapova said. "I got myself into the quarter-final of a Grand Slam. There is no reason I shouldn't be looking to improve and to getting my game in a better position than any other previous round. It's only going to be tougher, especially against Serena."
Williams, who advanced in 55 minutes, said she did not know she was facing Sharapova, who has not defeated her in more than a decade.
"I'll be ready, she had a good win," Williams said. "I have nothing to lose and we are both doing the best we can."
Fourth seed Agnieszka Radwanska, beat cramping German Anna-Lena Friedsam 6-7 (6-8), 6-1, 7-5 and will next face Carla Suárez Navarro, who faced knee problems in a comeback win over Australian Daria Gavrilova 0-6, 6-3, 6-2.
Sharapova, a decade older at 28 than 12th seed Bencic, put on a serving display with 21 aces. Sharapova took victory on a point decided by Hawk-Eye electronic line calling, with her ace ruled good.
"This must be the first (time) I've won a match on a challenge," the 2008 Melbourne champion, said. "I felt like I hit a clean ball. I was positive it was on the line. In the worst case, we go back to deuce."