Having maintained his record as a five-set specialist on his triumphant Australian Open return, Kei Nishikori vowed to work on getting wins sewn up earlier.

Featuring at the Melbourne Park slam for the first time since 2021, Nishikori got his campaign up and running with a thrilling 4-6 4-6 (4-7) 7-5 6-2 6-3 win over Thiago Monteiro on Sunday.

The 35-year-old – a four-time Australian Open quarter-finalist – saved two match points before launching his stirring fightback in front of a raucous crowd at John Cain Arena.

He has now won 26 of his 34 matches that have gone to five sets, including eight of nine at Melbourne Park, the exception coming against the great Roger Federer in 2017.

He will face either 12th seed Tommy Paul or home hope Christopher O'Connell in the second round, where he will hope to seal progress in quicker fashion.

"Well, I'm not thinking much because I just try to focus on what I have to do in the next point or next game," Nishikori said when asked about his five-set record.

"I think my focus level is always high, especially in the last set. Also, it's big for me to stay tough until the end.

"But the other side is, other people are winning in three sets but I'm not. I'm always going to fifth. That's something I have to work on, it's not a good habit to have!"

Nishikori is back in the ATP's top 100 for the first time since 2022 after finishing as runner-up at last week's Hong Kong Tennis Open, and he revealed he almost gave up on tennis when injuries forced him to miss nine straight slams between 2022 and 2024.

"I almost did [quit] last year because I had my knee and shoulder two years ago, and I almost came back. I got injured again. It was real up and downs," he said.

"I was thinking, 'if I have maybe another surgery, then mentally I don't think I'd be able to fight anymore'. It was like two in a row.

"I had a year I couldn't play and another half year I couldn't play because of an injury I got, so that was toughest time I think, the end of 2023.

Asked what kept him going, Nishikori said: "I just still love to play tennis. I love to compete. I wanted to play with big stadiums like today.

"That was my goal a year ago when I was doing rehab. I think I still have the chance to play with these top players. I was feeling that at the end of last year. I got more confidence.

"This last week also help me to believe in myself, so I'm still really enjoying this moment."