Kei Nishikori feels he is still coming to terms with life as world number five.
Kei Nishikori admitted he is not completely comfortable with his lofty ranking after beating Steve Johnson in four sets at the Australian Open on Saturday.
World number five Nishikori secured his third consecutive fourth-round berth at Melbourne Park after recovering from a slow start to account for Johnson 6-7 (7-9) 6-1 6-2 6-3.
The 25-year-old has more eyes on him than ever before, having reached the final of the US Open last year.
That run at Flushing Meadows culminated in his highest-ever ranking of fifth in the world - something he conceded continues to weigh on his mind.
"[Being number] five is different feeling than [being] outside the top 10 because you still feel lot of confidence, but you feel other things off the court," Nishikori said.
"I think I feel more pressure than before. I try not to think too much. But you obviously feel little bit.
"It's still not comfortable for me to be this ranking. But I think I need more time to get used to.
"If I can play good tennis, I think I have a lot of chance to stay here whole this year.
"You know, practice hard and prepare good. Yeah, hopefully I can do good this week and next week."
Nishikori was far from his best in the opening set on Hisense Arena before flicking the switch to quickly dispose of Johnson.
And the Japanese is determined to play in more big matches following his loss to Marin Cilic in last year's US Open final.
"I'm sure that I need more experience," added Nishikori.
"Especially like the US Open final - I was really nervous, I couldn't think anything and couldn't, you know, play good tennis. I need couple more those experience, for sure."