|ATP Finals 2020 - final|
|Venue: O2 Arena, London Date: 22 November Time: 18:00 GMT|
|Coverage: Watch live on BBC Two, BBC iPlayer, BBC Sport website and mobile app; follow BBC live text commentary online.|
Rafael Nadal and Novak Djokovic were knocked out of the ATP Finals as Daniil Medvedev and Dominic Thiem set up a title decider.
World number two Nadal served for the match at 5-4 in the second set but Russia's Medvedev hit back brilliantly to win 3-6 7-6 (7-4) 6-3 in London.
He was the more aggressive player throughout and was composed in the decider as errors came from Nadal.
Earlier, Thiem beat world number one Djokovic 7-5 6-7 (10-12) 7-6 (7-5).
The Austrian trusted his big hitting and fought back from a 4-0 deficit in the deciding third-set tie-break to win in almost three hours.
Unlike Thiem, Medvedev, who had never beaten Nadal, is unbeaten throughout the week at the O2 Arena.
Neither man has won the season-ending event before but Thiem will start Sunday's final as the narrow favourite, having won his first Grand Slam at the US Open in September.
Were world number four Medvedev to win, it would be the biggest victory of his career.
For 20-time Grand Slam champion Nadal, defeat ended his hopes of winning the tournament - one of the few prizes missing from his glittering CV - for the first time.
Medvedev outlasts Nadal on day for the next generation
It has been the burning question in men's tennis in recent years; when will the next generation replace Nadal, Djokovic and Roger Federer at the top of the game? There have been many false dawns, and this may be another, but Medvedev and Thiem were deserving winners.
Medvedev dictated against Nadal, hitting 42 winners to the Spaniard's 30 in his unconventional style.
The 24-year-old Russian set the early pace, creating opportunities on Nadal's serve and breezing through his own service games, only for his level to drop in the seventh game, allowing Nadal to make the pivotal break.
Medvedev did not panic and when Nadal's level dropped at the beginning of the second - an unforced error and a double fault gifted a break - he raced into a 4-1 lead in 15 minutes.
Medvedev then saw his lead wiped out as Nadal roared back but with the Spaniard champion serving for the set, Medvedev cut loose and played a near perfect return game to get back on terms.
Medvedev won the second-set tie-break - helped by a crucial framed forehand that lobbed Nadal - and in the decider he was the player applying all of the pressure.
Nadal's movement and power of shot slowed and after fighting off three breaks points, he could not deny the Russian a fourth time when he put away a smash at the net.
At that point the fight seemed to drain from Nadal and, serving to stay in the match, he double-faulted before hitting a forehand into the net on match point.
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Increased belief helps Thiem rally
Thiem, 27, has stepped up in recent months, winning his maiden Slam and producing some of the best tennis this week in London.
Against Djokovic, his belief in his shot-making and ability to play the big shot at the right moment proved pivotal.
He double-faulted on the opening point of the deciding tie-break and Djokovic raced into the lead before Thiem sliced his way back into contention.
A fifth match point was cancelled out by a Djokovic ace but Thiem's relentless backhand that hugged the baseline was key to his victory.
Djokovic has not been at his best in London and he cut a frustrated figure throughout the decider, letting out a furious yell when he sent an easy return of serve long at 30-30 on the Thiem serve in the third.
His groundstrokes were simply not as consistently composed as usual and his repeated moves to the net did not work.
Usually, a 4-0 lead in a tie-break for Djokovic would mean game over. Instead, he was out-hit and out-thought by his opponent.
"What he did from 0-4 in the third-set tie-breaker was just unreal. I don't think I played bad. I made all of my first serves. He just crushed the ball," said Djokovic, who had been chasing a record-equalling sixth title.
"I was in a driver's position at 4-0. I thought I was very close to winning it. He just took it away from me. But he deserved it, because he just went for it and everything worked."
Despite the loss, Djokovic finishes the year as world number one, having lost just five matches in 2020, and will now prepare to defend his Australian Open title in January.
BBC tennis correspondent Russell Fuller
No-one has managed to beat both Nadal and Djokovic at the ATP Finals since 2010.
Now Medvedev and Thiem have done it in the same year, and even beaten them together on the same day.
The next generation are consistently having more success against them on the ATP Tour.
Although that success has not yet translated to the Grand Slams in quite the same way, perhaps next year will be the year.
Like the semi-finals, the final could be very tight.
While Thiem is threatening to become the hardest man to beat on tour, Medvedev is brimming with confidence after recording nine November wins in a row.
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