After writing off his chances of winning the Australian Open prior to the tournament, Rafael Nadal hailed progressing to the quarter-finals as a "great result" on Sunday.

Nadal, a 14-time grand slam winner, earned an eighth successive last-eight appearance at Melbourne Park with a 7-5 6-1 6-4 victory over South African Kevin Anderson.

The Spaniard was slow out of the blocks, but eventually found his rhythm to set up a quarter-final meeting with seventh seed Tomas Berdych.

It is a confidence-boosting result for Nadal, who claimed before the Australian Open that he should not be considered among the favourites in Melbourne as he continues his comeback from appendix surgery.

"I am one of the eight. That's the most important thing, no? I am in the last eight of the tournament," Nadal told reporters on Sunday.

"Especially in this moment when you are coming back after a period of time where you were not on competition and you're going to play a very tough player like Tomas Berdych that he started the season great playing very well in Doha, and now he's here in quarter-finals.

"I don't know if he lost a set. I don't think so. He's playing great, will be a very tough opponent.

"But for me quarter-finals is a great result, talking seriously. Arriving here, losing in the first round of Qatar, not playing matches for the last seven months, to have the chance to be in quarter-finals again here is a very positive thing for me. I'm very happy for that."

Nadal added: "I am sure that going to help me for the next events. I am not a person that I am happy like this and that's it. No. I try to play better and better every day.

"If that happens, I hope to keep having chances for the next match. But [Sunday] is a day to be happy the way that I improved my level of everything, talking about tennis, all the things I have to do on court. I was closer.

"Even if I played the first two sets the other day well, [against Anderson] I was much closer what I have to do to try to have success."