THEME FOR THIEM, MEDVEDEV: UPSET

Instead of No. 1 Novak Djokovic vs. No. 2 Rafael Nadal for the ATP Finals trophy, it’ll be No. 3 Dominic Thiem against No. 4 Daniil Medvedev.

Nadal had won 71 matches in a row when grabbing the opening set, and he served for the victory in Saturday’s semifinals when leading 5-4 in the second set. But Medvedev broke at love there and came all the way back to win 3-6, 7-6 (4), 6-3, claiming the last four games.

“It’s great that we managed to beat two of the biggest players in the history of the sport,” Medvedev said. “It’s super for tennis.”

Thiem frittered away four match points in his semifinal against Djokovic because he was “tight and nervous” during a secondset tiebreaker. Thiem gathered himself, though, and eventually reeled off seven of the match’s last eight points after trailing 4-0 in the last tiebreaker, winning 7-5, 6-7 (10), 7-6 (5).

“What he did from 0-4 in the third-set tiebreaker was just unreal,” said Djokovic, a 17-time Grand Slam champion. “I don’t think I played bad. He just crushed the ball and everything went in.”

Thiem ended Djokovic’s bid for a record-tying sixth ATP Finals trophy, while Medvedev prevented Nadal from continuing to pursue the most significant title the 20-time major champ hasn’t won.

Instead of a 57th meeting between Djokovic and Nadal, Thiem and Medvedev will face off for the fifth time. Thiem leads 3-1, including a straight-set victory in the U.S. Open semifinals in September en route to the 27-year-old Austrian’s first Grand Slam championship.

“I, for sure, can cause him some trouble,” Medvedev said.

Did that to Nadal, too. Nadal seemed on his way to the final when he reeled off four consecutive games in the second set for a chance to serve for the match. He surprisingly stumbled.

“I played a bad game. That’s it,” said Nadal, who deflected a question about whether he had any physical issues during the match.

Once he was back in the match, Medvedev took advantage, dominating the ensuing tiebreaker with the help of a shanked lob winner, a forehand winner that concluded a 26-stroke exchange and a leaping backhand that drew a netted forehand.

Nadal couldn’t shake that off, dropping the match’s last three games as he serve-and-volleyed more than usual, sliced his backhand more than usual and made forehand errors more than usual.

Medvedev had been 0-3 against Nadal.

Whoever wins today will be the tournament’s sixth different champion over the past six years, the longest such stretch since 1974-79.