Kei Nishikori admits he needs to improve his overall game after surviving a big scare to come through his first round match against Kamil Majchrzak at the Australian Open.

The Japanese star was expected to make easy work of Polish qualifier Majchrzak but Nishikori was creeping towards a shock defeat in Melbourne.

Majchrzak claimed the opening two sets 6-3 7-6 (8-6) but the scorching temperature took its toll on his body as cramps started to set in.

Nishikori, who is priced at 29.00 to win the Australian Open, took advantage of the situation and responded to win the following two sets 6-0 6-2 and he held a 3-0 lead in the final set before his opponent retired.

The world number nine admits that he was lucky to get through the clash and insists he must step up his game for Thursday’s second round clash with Ivo Karlovic.

“I feel sorry for him,” said Nishikori. “I have to say he had it today. He was playing very well, better than I thought.

“It was very unfortunate how we finished, but I’ll try to do my best for the next round and hope I can play better. I was trying to play better every set, second set playing better but he was still playing amazing tennis, forehand, backhand, serving really well today.

“I have to be happy to go to the next round because I almost lost today.” Nishikori has won his three previous meetings with Croatia’s Karlovic without dropping a single set and will be confident of extending that impressive record on Thursday.