MELBOURNE, Australia (AP) ― Serena Williams’ long winning streak came to an end in an upset 4-6, 6-3, 6-3 loss to Ana Ivanovic in the fourth round of the Australian Open on Sunday.

Williams hadn’t lost a match since August, one of only four defeats in 2013, and came into the fourth round with 25 straight wins. It was her 70th match at Melbourne Park, a record in the Open era, and she’d already set the mark for most match wins ever at the Australian Open with her third-round victory.

Ivanovic hadn’t won a set in her four previous matches against Williams, who was a hot favorite to win a sixth Australian Open crown for her 18th Grand Slam title.

Williams has been almost perfect after winning the first set in Australian Open matches, losing only once in 52 previous matches after winning the opening set. But No. 14-seeded Ivanovic got on top early in the second set with some stunning forehand winners and never really let Williams back into the contest.

The 2008 French Open champion won by attacking the best serve in women’s tennis, frequently standing well inside the baseline to receive.

“It’s not easy, you know, playing such a champion ... but she is also just a human and I know she has lots of pressure, too.” Ivanovic said. “I just went out there swinging at the ball.”

Ivanovic had 33 winners, including 20 on her forehand side. Williams hit 22 winners but made 31 unforced errors.

The other quarterfinal will feature two women who’ll turn 32 next month, with two-time finalist Li Na beating No. 22 Ekaterina Makarova 6-2, 6-0 and No. 28 Flavia Pennetta upsetting No. 9 Angelique Kerber 6-1, 4-6, 7-5.