Australian wildcard Kimberly Birrell's long road to show court one in Brisbane meant she was never going to throw it in when a win against world No.10 Daria Kasatkina appeared to be slipping away.
The 20-year-old daughter of a Gold Coast tennis coach was trailing 3-5 in the third set in her Brisbane International debut, but rallied to break back and eventually prevail 5-7 6-4 7-6 (7-3).
"I was just telling myself to just keep fighting and keep asking the questions, because I knew she was going to ask the question every single point," Birrell said.
"I was just telling myself 'it's not over, it's not over' - and it wasn't."
She will be joined in the second round by Melbourne qualifier Destanee Aiava, who dominated proceedings against Kristina Mladenovic to win 6-3 7-6 (7-2) and complete a perfect start for the Australian contingent.
Birrell was born in Germany to Australian-born, tennis-playing parents who now run a club on the Gold Coast.
"We (Birrell and her brother) both fell in love with tennis and I'm very lucky to share a passion with my parents and we have an awesome relationship," she said.
"We dream about moments like this."
Birrell had won the Australian Open wildcard playoff final earlier this month to secure a spot at January's grand slam and maintained that form against the highly-fancied Russian on Monday.
Dropping an early break in the third set and then losing her serve at 3-4 wasn't enough to deter the Queenslander, who unleashed a series of crushing backhands to break twice herself and serve for the match at 6-5 on the same court she has trained on countless times.
Birrell was broken again, but played a fearless tie-breaker to claim the biggest scalp of her career in a battle that lasted three hours and eight minutes.
Earlier, Czech fifth seed and 2017 champion Karolina Pliskova rallied from a set and a break down to topple Yulia Putintseva 4-6 6-3 6-4.
Ukraine's Lesia Tsurenko had an easier time of it in her first-round clash with Mihaela Buzarnescu, prevailing 6-0 6-2.
She will play Birrell in the second round, while Aiava meets US Open champion and second seed Naomi Osaka.
Australian world No.157 Priscilla Hon was eliminated after losing to Brit Harriet Dart, ranked eight places higher, in three sets.
