Harriet Dart won five matches in total at Indian Wells including qualifying
British qualifier Harriet Dart lost in straight sets to American Madison Keys in the fourth round at Indian Wells.
Australian Open semi-finalist Keys won 6-1 6-4 against Dart, who is ranked 122nd in the world, in California.
Dart, 25, is on course to break into the world's top 100 for the first time following her run to the last 16.
Keys will face Iga Swiatek in the quarter-finals, after the Polish third seed came from a set down to defeat Germany's Angelique Kerber 4-6 6-2 6-3.
"This week has been an incredible turning point for me," Dart told BBC Sport.
"To try and not forget about the good matches that I have played this week is super important.
"I thought Madison played a great match today and I think she would have beaten most people. I was definitely a little bit flat - a sixth match was maybe a step too far."
Dart missed a break point in the opening game of the contest and that proved to be her only opportunity as 25th seed Keys ran away with the opening set.
The Briton survived break points in the first and fifth games as she sought to force a deciding set - but Keys, 27, broke to love for 5-4 before serving out the match.
However, her run at Indian Wells, which included victory over former world number three Elina Svitolina, will help her secure automatic qualification at future Grand Slams.
"Everyone knows qualifying for a Grand Slam is really tough," Dart said.
"You have to play three tough players, a lot who have formerly been top players but have dropped a little bit."
Also in the women's draw on Tuesday, Romanian two-time Grand Slam champion Simona Halep beat compatriot Sorana Cirstea in straight sets, winning 6-1 6-4.
Halep will meet Petra Martic - who knocked out British number one Emma Raducanu on Sunday - in the last eight, following the Croat's 7-6 (8-6) 6-4 victory against Russian Ludmilla Samsonova.
Spain's Paula Badosa continued her title defence with a 6-4 6-4 win over US Open runner-up Leylah Fernandez. She will face Veronika Kudermetova of Russia for a place in the semi-finals.
In the men's draw, Italian sixth seed Matteo Berrettini overcame South Africa's Lloyd Harris 6-4 7-5 to set up a fourth round meeting with Serbia's Miomir Kecmanovic, who beat Dutchman Botic van de Zandschulp 7-6 (7-3) 7-5.
American 20th seed Taylor Fritz beat Spaniard Jaume Munar 6-4 2-6 7-6 (7-2) and will face Alex de Minaur next, after the Australian defeated American Tommy Paul 7-6 (7-2) 6-4.
Britain's defending men's champion Cameron Norrie progressed to the last 16 on Monday. He plays American Jenson Brooksby on Wednesday.
