LONDON (AP) Two-time defending champion Novak Djokovic overcame a lapse of concentration to beat Kei Nishikori 6-1, 3-6, 6-0 and advance to a third straight final at the ATP Finals on Saturday.
The Serb, who sealed the year-end No. 1 spot after finishing unbeaten in the round robin phase, dropped his first set since the start of the tournament after losing his focus early in the second set, visibly angered by a partisan crowd.
''The crowd has a right to do what they want, to cheer for whoever they want,'' said Djokovic. ''Some individuals that were going over the line throughout the whole match, some provocations that I usually don't react on, but I did. It was my fault.''
But the fourth-seeded Nishikori failed to build on the momentum at the start of the decider when he missed two break points before Djokovic recovered and won the last six games.
Djokovic, who is bidding to become the first player since Ivan Lendl from 1985-87 to win the season finale three years in a row, will next face either Roger Federer or Stan Wawrinka, who play later in an all-Swiss semifinal.
Djokovic dictated play from the baseline in the first set and broke immediately at the start of the second as he looked poised for another easy win. But his game dropped off suddenly when he let the Japanese newcomer came back with a double fault that the crowd applauded.
Djokovic applauded in return with irony and shook his head in disbelief as he prepared to return Nishikori's next service game.
''I lost the concentration, I lost the break because of that,'' he said. ''I allowed myself to be in the situation to lose the set, maybe even lose the match. It was my fault and I should know better.''
Challenged for the first time this week, the top-ranked Serb could not channel his anger and struggled to recover as he hit just 3 winners to 8 unforced errors in the second set, with Nishikori playing with more confidence and hitting the lines.
After receiving treatment on his right wrist, the U.S. Open runner-up broke for a 5-3 lead following a spectacular point. After a sharp forehand attack, Nishikori dragged Djokovic to the net with a drop shot, before hitting a lob that offered him the chance to conclude with a crosscourt forehand winner, sending the crowd into rapture.
The turning point came in the first game of the third set, when Djokovic - who had lost just nine games in his three previous matches - faced two break points at 15-40. Nishikori, who upest Djokovic in the U.S. Open semifinals, could not seize his chance, hitting two consecutive unforced errors as the momentum swing the Serb's way.
''I was close, for sure,'' said Nishirkori, who finished the season as No.5 in the rankings. ''I think I started thinking too much about he's the No. 1 player.''
Djokovic showed no mercy afterward, extending his indoor unbeaten run to 31 matches.
''I was fortunate because in the beginning of the third set, he had breakpoints. If he broke me, the match could have gone either way,'' he said.