When Nishikori defeated the Serb to reach the US Open final it had a dramatic impact on his confidence.
Nishikori said: "It was one of the best matches I had last year against one of the best players on the tour.
"That US Open changed me a lot.
"I won two titles after that and I had a lot of confidence to beat him and also (Stan) Wawrinka, (Milos) Raonic – I had some great matches in the US Open so it was a great moment for me."
He added: "I've got great memories from this tournament and I played really good matches to win against Tomas (Berdych) in the final.
"I then lost to Rafa (Rafael Nadal) at the Australian Open but that was a great match so I was really happy with what I did last year."
Nishikori has been working with coach Michael Chang, and says Chang's insights have had a positive effect on his game.
He said: "He's been giving me some good tips to get better to go to the next level.
"He's a great coach – he's tough but he's given me great practice and I've had a great off-season.
"I think I'm ready for the Australian Open."