Defending champion Karolina Pliskova is out of the Qatar Total Open after being beaten by the American teenager CiCi Bellis.
Bellis, who had to qualify for the tournament, reached the quarter-finals by defeating Pliskova 7-6 6-3.
It was a desperately disappointing performance by the world number five who had her serve broken five times during the match.
Pliskova had easily beaten the 18-year-old last month in Brisbane and Bellis was pleased to gain her revenge.
She said afterwards: "This was huge for me. I think I played a really good match and just tried to track down as many balls as I could.
"Obviously, I've watched her play for many years and she's one of my idols for sure. I'm just really happy to be able to get through it.
"When I played her in Brisbane, she killed me, and I was super nervous before that match."
Bellis had already beaten Daria Kasatkina and Madison Keys in Qatar while Pliskova had spoken of feeling low energy levels coming into the match.
"I think it's definitely a milestone," Bellis added. "It's great, but you know, definitely move on to the next one and just start thinking about tomorrow."
Bellis will play the number two seed Simona Halep, who reached the Australian Open final last month, in the quarter-finals.
Halep is 1/1 to win the match in two sets and 14/1 to triumph at Wimbledon later this year.
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