The Spaniard took two hours and 10 minutes to secure his spot in the last eight, but remained coy on his chances of success in Melbourne.
"It was a tough match," said Ferrer. "I played really good in the first two sets and now I'm in the quarter-final of the Australian Open.
"It's really difficult [to say if I can win the tournament]. I never can say I will win a Grand Slam because it's very difficult.
"Now I want to rest and prepare for my next match."
Ferrer has never reached the final of a Grand Slam tournament.