Emma Raducanu was knocked out of the Miami Open by Canada's Bianca Andreescu after a thrilling first-round match that showcased the huge potential both players still possess.
The British number one, 20, lost 6-3 3-6 6-2 against 22-year-old Andreescu, who also won the US Open as a teenager.
A tight contest ran away from Raducanu when Andreescu won the last four games.
Two more Britons - Andy Murray and Kyle Edmund - play in the first round of the men's singles later on Wednesday.
Former world number one Murray, 35, plays Serbia's Dusan Lajovic about 21:00 GMT, while Edmund continues his comeback from a knee injury against China's Yibing Wu at a similar time.
Raducanu, ranked 72nd in the world, enjoyed a productive week in Indian Wells before moving on to Miami, having reached the last 16 in the Californian desert despite her preparation being hampered by a bout of tonsillitis and the recurrence of a wrist injury.
While her build-up in Florida was more conventional, landing a first-round opponent with the calibre of former world number four Andreescu was a tough draw.
The parallels between the pair are clear - primarily being teenage US Open champions who have been beset by injuries since, but also born in the same part of Canada with Romanian heritage.
And so it teed up an intriguing contest between two exciting players who reminded everyone of their considerable talent in an enjoyable encounter.
Raducanu, who won the New York title as a qualifier in 2021, was broken in her first service game of the match when she pushed a forehand wide and Andreescu moved 2-0 ahead with what proved to be a critical break in the opening set.
Former Miami finalist Andreescu continued to apply pressure on Raducanu's serve while dominating on her own, retaining composure to seal an opener which she had long controlled after the Briton had seen off three other set points.
Raducanu's unforced errors had far outweighed her winners but she found her rhythm in the second set, looking comfortable on serve and returning with more quality.
As the Briton moved 4-3 ahead with the set still on serve, her belief continued to grow.
She cranked up the pressure in a gripping eighth game, 31st-ranked Andreescu showing incredible resistance and resilience to save six break points, but eventually buckling and enabling Raducanu to take the match into a decider.
Both players took a long break before the decider - an indication of their mental and physical exertions - and the encounter resumed at the same intensity.
Raducanu was unable to break Andreescu's serve from 0-40 in the opening game and that proved crucial as the 2019 US Open champion quickly turned a tight battle in her favour.
Heavy coughing leads to injury for Swiatek
Meanwhile, defending women's champion Iga Swiatek has pulled out of the tournament on the eve of her first-round match with a rib injury.
Poland's world number one Swiatek, 21, says the injury was caused by heavy coughing from an infection and she will also miss her nation's tie against Kazakhstan in the Billie Jean King Cup on 14-15 April.
"Unfortunately, I'm still feeling a lot of discomfort and pain and I can't compete," said the reigning French Open and US Open champion.
"I will keep you updated about where I play next, because it depends on my process of recovering and the recommendation of my medical team.
"It's a truly difficult call to not play in Miami and BJK Cup, but health is the most important."