PHOTOS: Jessica Pegula pulls-off stunning upset at Australian Open

MELBOURNE, Australia (WBEN/AP) - Jessica Pegula has pulled-off a stunning upset at the Austrailian Open, building on her momentum from the end of last year, defeating 12th-seeded and two-time former Australian champion Victoria Azarenka 7-5, 6-4 to advance to the second round for the first time.

Azarenka required medical attention on court in the second set when she bent over in the middle of the game and appeared to have trouble breathing. After a medical timeout, she managed to hold serve and break Pegula to level the match at 4-all, but then lost the final two games.

The 26-year-old Pegula, daughter of Buffalo Bills and Sabres owners Terry and Kim Pegula, had her best-ever result at a major at last year’s U.S. Open, where she reached the third round. She also won two matches at last week’s Yarra Valley Classic warm-up tournament before losing to defending Australian Open champion Sofia Kenin in three sets.

Azarenka, who won the Australian Open in 2012 and 2013, was one of 72 players who were forced into hard quarantine after arriving in Australia. She played just one match after being released in late January.