LONDON » In a three-set victory, it all came down to one point.

Kei Nishikori won it, and the match.

The eighth-seeded Japanese player beat Tomas Berdych 7-5, 3-6, 6-3 today at the ATP finals for his first win at this week’s tournament — an encounter that will be followed by the big match between Novak Djokovic and Roger Federer later in the day at the O2 Arena.

The decisive point came with the score even at 3-3 in the third set. The sixth-seeded Berdych had his third break point of the match — after converting the previous two — but he put a backhand into the net after a long rally with Nishikori on the defensive.

"That was a really big point. He had three, four shots that he went really aggressive," said Nishikori, who reached the semifinals last year in his debut at the season-ending tournament. "I mean, last shot, I kind of went for it, closed my eyes. Was a little bit lucky I made that shot."

Berdych attributed the loss of the match to the loss of that point.

"The rally starts pretty well for me, but I was not able to break him. Then I lost my serve," said Berdych, who has already been defeated twice this week. "Basically, that was it. That was the difference today."

After holding serve, Nishkori broke his Czech opponent to take a 5-3 lead, and then served it out.

In the first set, Nishikori took the lead with a late break at love, and then held serve. He broke again to start the second set and led 2-0, but Berdych then won five straight games and eventually the set.

Nishikori is now 1-1 after losing to Djokovic on Sunday. He will next face Federer on Thursday.

"It’s going to be really important match for both of us," Nishikori said. "I have to win the next match to qualify (from) the group. So I (will) try to recover well today and tomorrow, and I will get good tactics ready and try to play another good match."