The Austrian is only the second player in 2020 to win a tie-break against Djokovic, who entered the third-set decider with a 15-1 tie-break record this season.
It will be Medvedev and Dominic Thiem in the final at the Nitto ATP Finals in London, after the 24-year-old Russian rallied past Rafael Nadal 3-6 7-6 (4) 6-3 on Saturday night to earn his first win over the Spaniard in four tries.
"The difference was that when you hit full power and everything goes in, it just goes in. I think he played some good points and I made a couple of mistakes", Nadal said. "I got so tight in the second-set tie-break, first of all because to play these legends is always going to be something special. But I guess it wasn't developed and it wasn't there because we just did not have the cases like this", said Djokovic, who used to be president of the ATP's player council before he resigned earlier this year.
During the current ATP tournament, Medvedev has been victorious in every one of his matches.
(MENAFN - NewsBytes) World number four Daniil Medvedev trounced veteran Rafael Nadal 3-6, 7-6 (7-4), 6-3 to reach the grand finale of ATP Finals. Hopefully I can play good like this. "He just took it away from me".
He said: "I've known Sascha (Zverev) for a very long time since he was very young". Dominic won his first slam, playing unbelievable tennis right now.
By the start of the third set, Medvedev had struck twice the number of total winners and made just three more unforced errors than Nadal, suggesting that Medvedev's aggressive, courageous play was additionally accurate. "But I had a big opportunity".
Nadal held and then broke Medvedev with some incredible passing shots and that world-famous determination of his which has made him the joint-most successful men's player in history. It is a awful shame that one player will not be remembered for their efforts this week but that makes for what should be an awe-inspiring contest between rather differently brilliant players.
After an aggressive start, Medvedev had three chances to break in game three, yet the Russian failed to take the opportunity to nose himself ahead. I lost semi-finals in Australia, which I could have won.
Their last meeting came at the semi-final of the US Open, with the Russian going down to Thiem.
20-time grand slam champion Nadal looked to be cruising after the first set, but was quickly down 3-0 in the second set.
"The first two times on Centre Court [I practised here] was with him", he said.
"We don't know what happened truly".
Earlier he had told a press conference: "I sincerely wish for him that he overcomes this soon and that he can focus on his life and tennis career". "I'm feeling confident. I think Rafa is also".