The old saying goes, "It ain't over 'til it's over" -- and Beatriz Haddad Maia learned that the hard way on Day 4 of the Australian Open.

Facing 16-year-old qualifier Alina Korneeva on Court 6, Haddad Maia had an amusing slip-up in what was otherwise a routine second-round match.

With Haddad Maia leading by a set and a break at 6-1, 3-2, the pair had one of their longest rallies of the match at 15-15. On the 28th shot of the point, Haddad Maia struck a forehand and turned her back to the court -- as she expected that her groundstroke had floated well long. 

But it hadn't. Instead, the ball dropped inside the baseline, and Haddad Maia had to hustle to her backhand side to retrieve Korneeva's next forehand.

She got there in time to foist up a high lob, which Korneeva let bounce before officially finishing off the rally with a forehand winner that just kissed the sideline.

The miscue did little to throw the No.10 seed off course, though she eventually had to save three break points in that service game to keep her lead. She finished off the victory 6-1, 6-2 to advance to the third round of the Australian Open for the first time.

Up next, she'll meet with another qualifier, Maria Timofeeva, who beat former champion Caroline Wozniacki.