AFP, MILAN: South Korea's Hyeon Chung kept his cool to upset top-seeded Russian Andrey Rublev and claim his first title at the Next Gen ATP finals in Milan on Saturday.

The bespectacled 21-year-old rallied from a set down to see off Rublev, the world number 37 who reached the US Open quarter-finals this year, 3-4 (5/7), 4-3 (7/2), 4-2, 4-2 in just under two hours.

Chung, ranked 54, sealed victory on his third match point after Rublev had saved two at 3-1 down in the fourth set of the final at the season-ending, eight-player tournament.

The former student of the Nick Bollettieri Tennis Academy in Florida -- who turned to a mental coach to help him deal with the pressure of tennis -- received $390,000 dollars (335,000 euros) but no world ranking points for winning the under-21 tournament. Chung revealed that his mind training had helped him in Milan, just days after he had suffered a first-round exit in Paris to Rafael Nadal.