Milan - Australian teenager Alex de Minaur reached the Next Gen ATP Finals championship match on Friday with a 3-4 (5/7), 4-1, 4-1, 3-4 (4/7), 4-2 victory over Spain's Jaume Munar.
De Minaur, 19, began the season at number 208 in the world rankings and reached a career-high 31 last month.
He now stands just one win away from capping his breakout season when he takes on top seed Stefanos Tsitsipas in Saturday's final.
De Minaur is now an impressive 28-22 on the year after entering 2018 with just two tour-level match wins to his record.
Seeded second, he has not lost a match at the tournament this week, winning Group B before battling past Munar in exactly two hours in the semi-finals.
Results from the ATP Next Gen Finals in Milan on Friday:
Stefanos Tsitsipas (GRE) bt Andrey Rublev (RUS) 4-3 (7/3), 3-4 (5/7), 4-0, 2-4, 4-3 (7/2)
Alex de Minaur (AUS) bt Jaume Munar (ESP) 3-4 (5/7), 4-1, 4-1, 3-4 (4/7) 4-2