London, July 8: World number one Ashleigh Barty was beaten for the first time in two months on Monday as Alison Riske claimed a superb fourth-round victory at Wimbledon.
The American, who had only reached this stage of a grand slam once before in her career, recovered to win 3-6 6-2 6-3 in 97 gruelling minutes on No.2 Court.
Having already beaten seeds Belinda Bencic and Donna Vekic at these championships, Riske will face either Serena Williams or Carla Suarez Navarro in her first major quarter-final.
Barty, who had not even dropped a set since the semi-finals of the French Open last month before this meeting, began with four consecutive aces as she battled to a 4-1 lead, before closing out the opening set as Riske missed a backhand return at the end of another love service game.
The Australian's backhand slice had been causing Riske some problems but she was off balance when her opponent responded with a string of emphatic ground strokes to move 4-1 ahead in the second set.
Riske then levelled the match with a simple passing shot after Barty, who won only two points at the net in set two, failed to do enough with a forehand volley.
A hard-fought third set swung Riske's way when she broke for a 5-3 lead with a fine forehand down the line, and last month's Libema Open champion claimed victory on her first match point as Barty sent a forehand into the tramlines.
"I've just been ready to battle every day I go out there and that's really shown in all my matches. I couldn't be more proud of myself," said Riske.
"I couldn't begin to say what it means to me. To overcome the matches the way that I have ultimately is what I'm most excited about. Being in the last eight at Wimbledon isn't too bad!"