Daniil Medvedev reached the final of the ATP Finals on Saturday for the first time in his career.
The Russian number four in the world was too strong for Rafael Nadal in the semi-final battle.
After a long game of more than 2.5 hours, there was 3-6, 7-6 (4) and 6-3 on the scoreboard in the O2 Arena in London.
Medvedev struck his first match point in the ninth game of the deciding set.
The 24-year-old Russian is only there for the second time at the prestigious end-of-year tournament.
Last year he played a supporting role by not getting past the group stage.
Nadal could have made it to the final of the ATP Finals for the third time, the tournament he never won.
In the final battle of 2010, the Spaniard lost to Roger Federer and three years later Novak Djokovic was too strong in the final of the prestigious end-of-year tournament.
Earlier in the day, Dominic Thiem had reached the final by eliminating world number one Djokovic.
The Austrian was too strong in a compelling fight with 7-5, 6-7 (10) and 7-6 (5).
Medvedev can book his second major tournament victory of the year in London.
He was previously the best at the Masters tournament in Paris.
In addition, he can take revenge on Thiem, who blocked his way to the US Open final earlier this year.
Rafael Nadal is disappointed after a lost point against Daniil Medvedev. (Photo: Pro Shots)
Rafael Nadal is disappointed after a lost point against Daniil Medvedev.
(Photo: Pro Shots)