Kei Nishikori reached the third round of the French Open on Wednesday having won back-to-back five-setters over a total of eight hours on court and admitted: "I feel like I've played five matches already." The 31-year-old needed four hours to see off Russian 23rd seed Karen Khachanov 4-6, 6-2, 2-6, 6-4, 6-4 on Court Philippe Chatrier. In the first round, he also needed four hours to beat Italian qualifier Alessandro Giannessi.
"I feel like I have played five matches already. Trust me, I hate playing five sets. I don't do it on purpose," said Nishikori, a three-time quarter-finalist in Paris.
The statistics tell a different story.
After also playing two five-setters in his only two matches at the 2020 tournament, he now has a record at the French Open of nine wins and two losses over the full distance.
In all, he has won 11 of his last 12 five-setters and has the best winning percentage rate of all active players.
"Today, my energy level was not great. I had a four hours first match, four hours today," he added.
"After the third set lost, I kept telling myself if I want to keep playing. There was no answer for me, but I just keep playing.
"My body said no, but my mind was just 'keep playing'. So I was able to win the fourth set without thinking anything."
Overall, Nishikori's five-set record in his career stands at 26-7.
Key for him now is to press on and convert his undoubted stamina into a late period of sustained success in a career which has so far yielded 12 titles.
"Everybody tells me I have a good record. Sometimes I have to think that I have to keep building my record after going five sets.
"I think in fifth sets I'm really playing good tennis, more than any other sets."
A former world number four, 2014 US Open runner-up Nishikori is playing in Paris on a ranking of 49, his lowest since 2011.
However, it has taken some serious hitters to subdue him in this European clay court season.
World number six Alexander Zverev defeated him in Madrid and Rome.
In between, he took a set off Rafael Nadal before losing in three sets in Barcelona.
"I only lost to top-10 players. You can say I'm not beating top-10 players right now, but I think things are getting much better for me," said Nishikori.
"I think I'm on the way to the top 10 again. I'm really enjoying this moment."
Regardless of how far he gets at the French Open -- he plays Swiss qualifier Henri Laaksonen next -- Nishikori won't have a lot of time to dwell on his form.
His wife Mai is expecting their first child later this year.
"I'm still thinking about the name of my child. It will be a Japanese name," he said.