SYDNEY, Australia - In her second career WTA main draw match, Australian wildcard Ellen Perez advanced past No.5 seed Kristina Mladenovic in the first round of the Sydney International, as the Frenchwoman succumbed to heat illness in the second set. 

The World No.343 was leading the match 6-4, 4-2, as the two played nearly 67 mintues on the Ken Rosewall Arena before Mladenovic could no longer continue. 

Though not how she would've wanted it, the victory is Perez's first against a Top 50 player, having also earned her first Top 100 win in Sydney a year ago, when she knocked off then-No.98 Kateryna Kozlova in qualifying. 

"I hope she gets a bit better - she looked like she was a little sick. It's unfortunate for her and it's never how you want to win, but it's always nice to get my first win. It's my first WTA main draw win, so I'm super excited," Perez said after the match. 

"I've actually always enjoyed the heat - I've been in America training in Georgia where it's hot and humid, and it's always been hot here in Australia. Physically, I feel really good. I felt like I could keep going. I was hydrating well, so that was nice."

Perez, a 22-year-old left-hander who played three seasons of collegiate tennis at the University of Georgia before turning professional, played her first WTA main draw match as a wildcard at the US Open in 2016, where she fell to Zhang Shuai.

Perez handled sweltering conditions in Sydney better than the World No.11, using a swinging serve and showing good instincts at the net to keep points short.

The wildcard set the tone with a love break in the first game of the match, though she needed some insurance in the seventh to see her way through to a one-set lead, and used another break in the first game of the second set to stay ahead until Mladenovic was forced to retire.

"I probably was a little nervous out there," Perez said about the tennis in the match. "I was missing a fair bit, but it was what she was giving me as well. I think I did what I needed to do to be up in the scoreline."

For Mladenovic, the defeat is her 14th straight in WTA matches, having not won since the Citi Open last July. 

An all-Australian second round could be on the cards for Perez next, as she'll face the winner of Ashleigh Barty or a to-be-determined qualifier.