Sloane Stephens produced a complete display to land a shock first-round win over two-time champion Petra Kvitova on day one of Wimbledon.
The American repeatedly made Kvitova work in the opening set, which she took 6-3 after two breaks of serve.
A key moment arrived in game six of the second when Kvitova - leading 3-2 - squandered four break points.
Stephens ruthlessly broke the Czech's serve in the next game and progressed, taking the second set 6-4.
Stephens will now play compatriot Kristie Ahn, who beat Britain's Heather Watson late on the opening day.
Two-time Grand Slam champion Tracy Austin described Stephens' opening display as "flawless".
Stephens, the 2017 US Open champion, said: "Seeing the first round I thought, 'oh boy, this will be a difficult task'.
"It's been a couple of years since I've had a good result on grass. Here is a good start beating a really good grass-court player."
Stephens - ranked 63 places below world number 10 Kvitova - looked consistent in all aspects of her game in this Centre Court battle between two previous Grand Slam winners.
By contrast Kvitova - champion at SW19 in 2011 and 2014 - seemed to struggle with her timing and a number of mis-hits featured in her play on a day when she made 20 unforced errors.
Meanwhile day one's rain-disrupted schedule meant Venus Williams' and Czech eighth-seed Karolina Pliskova were unable to play their respective matches but other seeded players got their tournaments under way.
American fourth seed Sofia Kenin beat China's Xinyu Wang 6-4 6-2, while Poland's seventh-seed Iga Swiatek overcame Hsieh Su-wei of Chinese Taipei 6-4 6-4.
Spain's Garbine Muguruza - 11th seed and the 2017 champion - dropped one game on her way to a 6-0 6-1 win over France's Fiona Ferro, while Kazakhstan's Elena Rybakina proved too strong for France's Kristina Mladenovic, winning 6-4 6-0.
Two of the top three women's players are not competing at Wimbledon, with four-time Grand Slam champion Naomi Osaka and defending champion Simona Halep absent.
Romania's Halep, who pulled out with a calf injury on Friday, announced on Monday that the problem would also rule her out of next month's Tokyo Olympics.
Elsewhere Andy Murray recomposed himself to ensure his Wimbledon singles return ended with a dramatic four-set victory over 24th seed Nikoloz Basilashvili.
In his first singles match in SW19 since 2017, the two-time champion led 6-4 6-3 5-0 against the Georgian.
The Briton could not convert two match points and wobbled as Basilashvili, 29, fought back to force a fourth set.
After a break to shut the Centre Court roof, Murray returned reinvigorated to win 6-4 6-3 5-7 6-3 under the lights.