Rafael Nadal reflected on being "a little bit lucky" to win a crucial first-set tie-break after he progressed to the Australian Open quarter-finals.

Nadal saw off Adrian Mannarino 7-6 (16-14) 6-2 6-2 on Sunday to seal his place in the last eight of the season's first grand slam for the 14th time.

The 20-time major winner, however, needed to overcome a stern challenge in the first set, winning a 30-minute tie-break.

Indeed, Nadal had to claw back four set points in the tie-break, before an early break in the second paved the way for a much simpler time from then on in against an opponent who had played late into the night in the previous round.

"The first set had been very, very emotional," Nadal said. "Anything could happen there. I was a little bit lucky at the end.

"Everybody knows how mentally [tough] this game is.

"It was a tough one and after that crazy first set, I think it was so important the break at the beginning of the second set.

"His ball was very difficult to control, very flat, very fast. I'm very happy that I survived that first set, without a doubt."

Nadal has only won the Australian Open once before, back in 2009, but his quest to land a record 21st grand slam title is going well so far.

"In this tournament I think I have been in a very good position to fight for it a lot of times in my career," Nadal added.

"I've always enjoyed playing in it a lot of times in my career. It's true that I was a little bit unlucky with injuries here, and sometimes I was unlucky because my opponents were a little bit better than me!

"But I've always enjoyed it and I'm very happy to be back in a quarter-final, it means a lot to me."

The Spaniard's hopes received another boost on Sunday, when world number three Alexander Zverev was knocked out by Canada's Denis Shapovalov, who will be Nadal's quarter-final opponent.

It will mark the fifth contest between 22-year-old Shapovalov and Nadal, with the latter having won three of their previous encounters.

"Shapovalov is a player with amazing potential," Nadal said.

"Everybody knows that when he's playing well, it's very difficult to stop him with [his] big serve, amazing forehand, and he's very quick."