LONDON (AP) -- Dominic Thiem ended Novak Djokovic's bid for a record-tying sixth ATP Finals title, beating the top-ranked player 7-5, 6-7 (10), 7-6 (5) in the semifinals Saturday by grabbing seven of the last eight points.
Thiem could have closed things more than an hour earlier, but he frittered away four match points in the second-set tiebreaker, including one by double-faulting.
Then the U.S. Open champion trailed 4-0 in the last tiebreaker before turning things around. When it ended with Djokovic sailing a forehand long, Thiem dropped his racket and covered his face with his hands.
''It was, for sure, a mental battle,'' Thiem said.
The No. 3-ranked Thiem's 300th career match win put him in the final of the season-ending tournament for the second straight year; he was runner-up to Stefanos Tsitsipas in 2019.
No. 2 Rafael Nadal was scheduled to face No. 4 Daniil Medvedev in Saturday's second semifinal. The final is Sunday. None of the last three men in the field has won the tournament, meaning there will be a sixth different champion over the past six years, the longest such stretch since 1974-79.
It's the first time since 2004 - when Roger Federer, Andy Roddick, Lleyton Hewitt and Marat Safin did it - that the top four players in the rankings filled the four semifinal slots for the ATP Finals.
This year's group is quite a quartet: They combined to win the past 10 Grand Slam men's singles titles and the last nine Masters 1000 trophies.
Djokovic, already assured of finishing the year ranked No. 1 for a record-tying sixth time, was trying to match Federer's mark of six ATP Finals trophies. A title also would have made Djokovic, at 33, the oldest champion in tournament history; Federer was 30 in 2011.
In Saturday's rematch of February's Australian Open final, in which Djokovic beat Thiem in five sets, there were plenty of long baseline exchanges on the indoor hard court - where things were quiet because spectators were banned due to the coronavirus pandemic - and few break chances for either player.
Thiem faced three break points and saved them all, quite an achievement against supreme returner Djokovic. And while Thiem managed to produce only a pair of break points, he used one of those to take a 6-5 lead in the opening set.
In the second, Thiem's ace put him ahead 6-5 in the tiebreaker, one point from victory.
But Djokovic saved that initial chance with a 127 mph service winner. Thiem's next opportunity to win came at 7-6, but he double-faulted. The third was at 9-8, when he pushed a down-the-line forehand wide. And then, at 10-9, Djokovic erased No. 4 with a forehand that landed right on a line.
That began a three-point run by Djokovic to steal the set and prolong the match. He needed four set points in all to do so, but came through when Thiem netted a backhand.
Afterward, Thiem acknowledged he was ''tight and nervous'' in that section. He regrouped, though, and came through in the clutch an hour later.
Thiem is now only the second man with at least five victories each against Djokovic (5-7 career mark), Nadal (6-9) and Federer (5-2). Andy Murray is the other.
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