Borna Coric, one year removed from his US Open junior title, made a victorious return to Flushing Meadows on Tuesday with a win in the first Grand Slam match of his career.
The 17-year-old Croatian, who came through qualifying to earn his main draw spot, was a convincing 6-4, 6-1, 6-2 winner over 29th-seeded Czech Lukas Rosol -- who claimed his second career ATP title at Winston-Salem last week. (Also Read: Federer Eases Into Second Round)
"It's an amazing feeling," said Coric, who arrived in New York with the goal of making it into the main draw.
"I said to myself, 'If I achieve that, that's going to be perfect.'
"Now actually winning a guy who is top 30, it's just unbelievable."
The upset put Coric into a second-round clash with history-making Victor Estrella Burgos, the Dominican Republic's first Grand Slam participant who is making his US Open debut at 34.
Age isn't the only thing separating the US Open debutants.
While Coric is still ranked only 204th in the world, he's tipped as a potential star.
He won his first ATP Tour level matches in Umag this year, and is expected to continue his climb up the rankings and join such teen sensations as Nick Kyrgios in challenging the game's established champions.
He has also been able to call on the support of successful compatriots on the tour as he negotiates the move from the junior ranks to the elite pro level.
Former Croatian stars Goran Ivanisevic and Ivan Ljubicic and current ATP player Marin Cilic have all offered help and advice, Coric said.
"I'm so thankful also to them because they helped me a lot. You know, I didn't know him so much, (but) they help me a lot."
Estrella Burgos, meanwhile, has had a bumpy ride since turning pro 12 years ago.
He took a break from competition to turn his hand to coaching, returning to tournament play in 2006, first on the Futures circuit and then on the developmental Challenger level.
A right elbow injury had him thinking about retirement in 2012, but his perseverance paid off when a Challenger Tour win in Ecuador in March saw him break into the top 100 in the world rankings.
While he can't draw on the support of fellow pros from his homeland, Estrella Burgos, now ranked 80th, had plenty of support from the crowd in New York, which boasts a large Dominican population.
"When I got on the court it was a very good feeling," Estrella Burgos said, although he said some of the well-meaning "out" calls from his new fans made for confusion.
"I was a little nervous when I was serving at match point, especially in New York where there's a lot of Dominican people coming to support me. When I was serving the last point, I was almost crying," he said.