NEW YORK, NY, USA - Russian qualifier Anna Kalinskaya scored the biggest win of her young career - and first over a Top 10 player - on one of the game's biggest stages, stunning 2017 US Open champion Sloane Stephens, 6-3, 6-4 to reach the second round at the USTA Billie Jean King National Tennis Center.

"I’m very happy with my win," Kalinskaya told the press, after her victory. "I’m very happy that I played on this court and I really enjoyed the atmosphere being there."

"That’s what I practice for: to play against big players on the big courts," the Russian added. "I think that’s what every player practices for."

Read more: Kalinskaya emulates 'idol' Myskina at US Open

The 20-year-old won three matches at the US Open's Qualifying Tournament to make the main draw for a second straight year, and sealed her first major main draw win with a searing backhand down the line after one hour and 23 minutes on Arthur Ashe Stadium.

"I just tried to focus on my game, don’t think too much about the other person, and just do my best," said Kalinskaya.

Stephens recently reunited with longtime coach Kamau Murray in the hopes of kickstarting an up and down 2019 season, and traded early service holds with Kalinskaya, who quickly adjusted to the glare of US Open spotlight.

Breaking at her first opportunity, the Russian, who is coached by former WTA player Patricia Tarabini, saved a break point in the next game to serve out the opening set, and shook off losing the early break in the second to hold steady with Stephens until the ninth game.

Kalinskaya narrowly lost to then-World No.9 Julia Goerges in her last US Open main draw appearance, and perhaps channeled that experience as she broke Stephens more and clinched the upset on her third match point.

Standing between the youngster and the third round is American wildcard Kristie Ahn, who stunned Western & Southern Open runner-up and 2004 US Open champion Svetlana Kuznetsova in straight sets earlier in the evening on Court 5.