Ana Ivanovic extends her winless streak against Top 5 opponents to 13 matches with a 4-6, 6-3, 6-4 loss to Victoria Azarenka in the fourth round of the U.S. Open. The former world No. 1 has not beaten a Top 5 player since defeating then-No. 4 Caroline Wozniacki in Indian Wells last year and has lost all eight meetings against Top 5 players this year, four of them in three sets. That includes a three-set loss to Azarenka five weeks ago in San Diego.

Before facing world No. 2 Azarenka, Ivanovic admitted she found it hard to recall her last "big win." She added, "That's a scary thought."

But after Tuesday's match, Ivanovic said that playing Azarenka so close was a good sign.

"It's very encouraging, because I know I'm right there with them," said Ivanovic. "It's definitely a lot of positives to take from this week and this match. It just wasn't quite the same as getting a win. It still doesn't change -- it's disappointing and it hurts."