Stefanos Tsitsipas confirmed his meteoric rise into the highest echelon of men's tennis by battling back to beat Austrian Dominic Thiem 6-7(6) 6-2 7-6(4) in a compelling title duel at the ATP Finals on Sunday. Tsitsipas, who beat Roger Federer in straight sets in the semi-final, is the youngest winner of the tournament since Lleyton Hewitt won it in 2001, aged 20. Thiem edged an intense first set full of powerful baseline rallies but Tsitsipas, the first Greek player to qualify for the ATP's blue-riband event, was undaunted and responded in style. As Thiem's level dipped, Tsitsipas surged into a 4-0 lead in the second set and then led 3-1 in the decider. Twice French Open runner-up Thiem was not finished though and fought back to take the match into a tiebreak. World number six Tsitsipas, the crowd favourite, led 4-1 but was pegged back to 4-4 before reeling off the last three points, sealing victory when Thiem ballooned a forehand wide. It is the fourth successive year the tournament has had a first-time winner and incredibly it is just one year since Tsitsipas won the NextGen Finals title for the best up-and-coming players on the men's Tour. After a sensational week in London, Tsitsipas looks poised to lead the charge for the young guns in 2020. "It's truly magnificent this final we put out today," Tsitsipas said. "I think it makes our sport great, tennis is all about this. "It's been a roller-coaster. Holding this trophy is amazing. "I have no clue how I played so well in the second set. " "I was nervous playing in such a big event, but I'm so relieved by the outstanding performance and the fight I showed today." Tsistipas was the youngest player to reach the final on debut since American Jim Courier in 1991.