In his first major match since the 2021 US Open, Nishikori prevailed past qualifier Gabriel Diallo in a four-hour 7-5, 7-6(3), 3-6, 1-6, 7-5 marathon on Sunday night.
As a result, the 34-year-old moved to 28-7 in career five-set matches. His 80 per cent win ratio is the best among active players on the tour, just pipping Adrian Mannarino and Novak Djokovic (both 78 percent).
His desire and commitment cannot be questioned.
"Winning is one thing, but I'm most happy that I've somehow gotten back to playing," the current world No.350 said. "It was big for me that my body could take a match like that.
"In Miami, I couldn't do anything and was nervous, but it was my first game in a long time, so I couldn't do anything, I couldn't attack, I didn't have much sense, so I couldn't hit as hard as I could.
"It's been a long time since I last played, it was five sets, so my fitness wasn't quite ready. Although I didn’t play that well, I didn't feel like I was going to make that many mistakes. This gives me a lot of confidence, it's already better than Miami."