Tsitsipas is Next Gen ATP champion

The 20-year-old Tsitsipas, ranked 15th in the world, came through 2-4, 4-1, 4-3 (7/3), 4-3 (7/3) against 19-year-old de Minaur after one hour and 41 minutes.

Greece's Stefanos Tsitsipas poses with the Next Gen ATP trophy after defeating Australia's Alex De Minaur in the final.

Greece's Stefanos Tsitsipas capped a breakthrough season by rallying from a set down to beat Australian Alex de Minaur in the Gen Next ATP final.

The 20-year-old Tsitsipas, ranked 15th in the world, came through 2-4, 4-1, 4-3 (7/3), 4-3 (7/3) against 19-year-old de Minaur after one hour and 41 minutes for his second title after Stockholm last month.

Tsitsipas, one of the sport's most improved players this year after starting the season ranked 91st, also finished runner-up to Rafael Nadal in Barcelona and Toronto.

The top seed claimed the title by winning all five of his matches during the week, to succeed South Korea's Hyeon Chung, who won the inaugural edition last year in which Tsitsipas only played an exhibition match.

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“It feels great. I've been playing some great tennis this week here in Milan,” Tsitsipas said.

“I stayed calm although I had a chance twice to win the match, but remained calm. I was aiming to win that match. I was mentally very strong and that was proven in the tie-break in the last set.”

Second seed de Minaur — who began the season at number 208 in the world rankings and reached a career-high 31 last month — had been undefeated until the final.

And he pushed Tsitsipas, who had been poised to snatch victory in the fourth set with a 3-2, 30/40 lead on the Australian's serve.

But a missed forehand, followed by a lunging backhand volley by de Minaur saved two match points to force a tie-break.

Tsitsipas made no mistake on his third, though, after the Australian sent a forehand long.

“Overall I'm very happy with my performance,” said the player from Sydney.

“All credit to Stefanos. He was a better player today.”

He added: “And I'm very happy it's over. It's been a long season, a season I'll never forget.

“I've played some incredible tennis throughout the whole year. And both mentally and physically, I feel like it's time to take a break. But really proud with myself, and I really owe it all to the team of people I've put around me.”

The round-robin tournament for players aged under 21 years has a shorter format than other tournaments, playing sets of first to four games, with tie breaks at 3-3.

It is designed to increase the number of pivotal moments in a match, while playing best-of-five sets does not alter the number of games required to win a match (12) from the traditional three-set scoring format.