Kei Nishikori believes that he is slowly beginning to produce his best tennis after seeing off Ivan Dodig in four sets at the Australian Open.

Last year's US Open runner-up was almost taken to five sets by the Croatian in their second-round contest, but after reaching the last 32, the Japanese star is confident that he will continue to improve in his next match.

The 25-year-old told reporters: "I think that I'm getting close. Maybe these couple matches didn't see me play 100%, but I still had good three-set and four-set wins.

"I think it's getting there. I'm playing good. For sure, this match will help for the next match. You know, try to be 100% little by little."

Nishikori will play American Steve Johnson in the third round on Saturday.