Kei Nishikori admits his body is hurting after a tumultuous season that has seen him establish himself as a potential Grand Slam winner, but he has one last mountain to climb.
That will come in London in eight days' time when the speedy Japanese star becomes the first Asian-born player to contest the prestigious ATP World Tour Finals, better-known as the Masters of men's tennis.
Nishikori, who reached the final of the US Open in September where he lost to Marin Cilic, made sure of his ticket to London on Friday when he defeated David Ferrer in the Paris Masters quarter-finals.
That match lasted two hours and 43 minutes and ended half an hour after midnight, less than 17 hours before the 24-year-old took to the Bercy Indoor Arena court once again to take on the world's best player, Novak Djokovic, in the semi-finals.
His exhausting win over Ferrer came after successive three-set battles against Tommy Robredo and Jo-Wilfried Tsonga and predictably Nishikori was spent.
Djokovic, coming off a couple of weeks off to mark the birth of his son Stefan, dominated from the start winning 6-2, 6-3 in just 62 minutes against a leaden-footed opponent, shorn of his biggest weapon -- his speed about the court.
Nishikori knew he was in trouble from the first exchanges.
"Yeah, maybe I was a little bit tired. You know, my body wasn't 100% ready for today's match. I had three tough matches before here, and my serve wasn't 100%," he said.
"I think I got home like 2:30 and had a massage. It's not easy after finishing like at 2:00 here and having to play today."
Still, Nishikori said he was happy with his week's work, having never got past the third round in Paris in three previous appearances in the French capital.
And he had no doubt that with a few days of rest he would be ready to take on the challenge of playing in an elite eight-man field.
"I'm really excited to go to London next week. First time to reach the finals," he said.
"It's going to be a lot of tension and I might get nervous first match, but I will try to enjoy the moment.
"I have been playing really well this year, so I think I have a chance to do well. Hopefully I can recover well next week and try to be ready for London."
There were words of encouragement too from Djokovic, who lost in four sets to Nishikori in a US Open semi-finals stunner and who entered Saturday's match with a losing 1-2 record against the Japanese player.
"He still is a young player, but definitely experiencing the best season of his life. He has won, I think, four titles if I'm not wrong. Played the final of the US Open," he said.
"So he showed that he can win against anybody really. He's an all-around player and very, very quick. One of the quickest players on the tour. Very aggressive. Very solid from both forehand and backhand side.
"So not much flaws in the game. I think he has improved since he started working with (coach) Michael Chang."