Ash Barty has become the latest high-profile casualty at the WTA's Charleston Open but was content with her run to the quarter-finals in preparations for next month's French Open.
World No.1 Barty dropped her serve five times in her 6-4 6-3 defeat to the unseeded Paula Badosa, while failing to make the most of her opportunities.
The Australian hit 34 winners to 19 but made twice as many unforced errors as the Spaniard, 24 to 12, and could only convert two of 14 break-point chances.
"I think I took a few too many risks in the match," Barty said.
"But I think it's been an exceptional three weeks to start off our trip and we can nothing but the positives from it."
Barty was the last remaining of the top eight seeds at the opening clay-court event on the WTA calendar this year.
Coming off her tournament win on the hardcourts of the Miami Open, Barty admitted earlier this week it was a quick turnaround to change surfaces.
And it proved to be too tough an ask on the green clay in South Carolina against world No.71 Badosa, who secured the biggest win of her career.
With the score at 3-3 in the second set, Badosa broke Barty's serve twice including in the final game of the match.
"I'm still a little bit shocked. I can't believe what just happened," Badosa said.
"When the ball went out, I was like 'What just happened right now?'"
For a place in the final, Badosa will face 15th-seeded Veronika Kudermetova, who ousted 2016 champion Sloane Stephens 6-3 6-4.
Ons Jabeur snapped a five-match losing streak in WTA quarter-finals to defeat Coco Gauff for the first time.
The 12th-seeded Tunisian eased past the teenage American 6-3 6-3 to be the highest-ranked player in the final four.
Jabeur will play unseeded Montenegrin Danka Kovinic, who reached her first WTA semi-final in five years, with a comeback win over Yulia Putintseva.
The near three-hour battle went the way of Kovinic 6-7 (2-7) 7-5 6-1.
"I really think this clay suits me well," she said.
"I just feel really, really good here."
All four semi-finalists are aiming to secure their maiden WTA title.