Former champion Stan Wawrinka emerged from a mid-match loss of confidence to battle past Russian fourth seed Daniil Medvedev to reach the Australian Open quarter-finals with a 6-2 2-6 4-6 7-6(2) 6-2 victory on Monday.
Medvedev, 23, arrived in Melbourne after a 2019 season featuring four titles and a Tour-leading 59 match wins and came into Monday's contest against Wawrinka having won both career meetings at Grand Slams in four sets.
But the Russian failed to find a way past the battling 2014 Australian Open champion, ending up the highest seed to fall in the men's draw so far.
Wawrinka, who won the last of his three Grand Slam titles at the 2016 U.S. Open, hit a staggering 71 winners and sealed the contest after three hours and 25 minutes.
"This was another amazing match, really tough to play against Daniil, I lost to him in U.S. Open but today came back strongly on the fourth and fifth sets," he said.
"The level was super high and it was a great atmosphere. It's amazing to keep playing here, I'm really happy to be able to continue to play at this level here and I'm looking forward to the quarter-final."
Wawrinka was flawless in the opening set and wrested initiative with a double break of the Russian's serve.
But Medvedev, who lost to Rafa Nadal in five sets in last year's U.S. Open final, levelled the contest by breaking Wawrinka twice in the second and nosed ahead in the match with a break in the seventh game of the third.
The points grew longer in the fourth with both players refusing to yield and it was only in the tiebreaker that Wawrinka created a clear margin to force a deciding set.
Wawrinka rode the momentum and broke Medvedev's first service game in the fifth, and another break in the seventh sealed the contest in his favour.
After his win, the 34-year-old tapped the side of his forehead with his finger and patted his chest as the crowd at Margaret Court Arena cheered him on.
"I'm finding the answers, I lost confidence a bit in the second and third sets but I knew it was all on the mental side of things," he said.
Wawrinka will meet either German seventh seed Alexander Zverev or 17th seed Andrey Rublev of Russia for a place in the semi-finals.