Kirsty Wigglesworth/Associated Press
LONDON — A year ago, Stefanos Tsitsipas won the NextGen Finals, the showcase tournament for players 21 and younger that is meant to be a harbinger of future greatness in men’s tennis. In Tsitsipas’s case, the future is now.
In an up-and-down final on Sunday, he rallied and held on to beat Dominic Thiem, 6-7 (6), 6-2, 7-6 (4), and win the ATP Finals, the most significant title of his young career. At 21 years 3 months, Tsitsipas became the youngest champion of the year-end event since 20-year-old Lleyton Hewitt won it in 2001.