British number one Heather Watson pulled off the biggest win of her career in Indian Wells, beating world number eight Agnieszka Radwanska.
Watson, 22, who had never previously taken a set off the 26-year-old Pole, won 6-4 6-4 in the third round at the BNP Paribas Open.
It is the first time in 12 attempts that Watson, ranked 43, has beaten a player in the world's top 10.
"I knew I had the tennis in me but I needed the belief," she said.
Watson will play Spanish 12th seed Carla Suarez Navarro in round four.
"I've had close matches with top 10 players," added Watson, who lost to Radwanska in last year's second round in California.
"I've also been wiped off the court by Radwanska - she's the main one who's beaten me very comfortably every time we've played."
|BBC tennis correspondent Russell Fuller|
|"This was a fine all-round performance from the British number one. She can take great heart in having outlasted a Wimbledon finalist in many of the baseline rallies."|
After being broken early on, Watson went on to dominate the opening set, breaking her opponent twice and regularly getting the better of some lengthy backhand exchanges.
The Briton produced a blistering ace to wrap up the set and then broke her opponent at the start of the second set as she moved 2-0 up.
Radwanska, last year's beaten finalist, belatedly found some form and hit back, breaking twice to move 4-2 ahead.
But Watson, who had never previously been further than the second round in Indian Wells, recovered her composure to win four straight games herself.
Leading 5-4, she served out to love to wrap up a superb victory and reach the last 16.
Radwanska said: "I thought she was serving really well in the important moments.
"I had some break points that could have made things different, especially in the second set, but she was too solid."
Meanwhile, world number one Serena Williams continued her winning return to Indian Wells, defeating Kazakhstan's Zarina Digas 6-2 6-0.