Kei Nishikori has admitted that he still needs time to "feel comfortable" with being ranked in the top 10.
The Japanese player, who beat David Ferrer to book a place in the quarter-finals, is the fifth seed at the Australian Open.
The 25-year-old told reporters: "I just need time to stay at this ranking to feel comfortable, I'm new to it and just need some more experience. If I can play like this I can stay top in the top 10."
Nishikori, who played in his first Grand Slam final at last year's US Open, faces defending champion Stanislas Wawrinka in the last eight in Melbourne.
