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 quarterfinals 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 eight-player tournament.
"After losing the first set, and down one break in the second, I was really nervous, really angry, but I tried to have a poker face," said Chung.
"I'm trying to create an image of being really strong mentally and I starting playing better and better," he said.
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.
"The coach says all the time, first try to stay calm and in control, to have a chance to play better and better."
It was Chung's third victory over Rublev. He beat the Russian earlier in the week and also at Winston-Salem on the ATP Tour in August.