Emma Raducanu said she felt “mentally and emotionally exhausted” after losing in the first round at the Madrid Open.
The 21-year-old was beaten 6-2 6-2 by Argentine qualifier Maria Lourdes Carle.
Raducanu helped Britain beat France in the Billie Jean King Cup before reaching her first WTA quarter-final in 19 months at the Stuttgart Open last week as she continues her comeback from an injury-hit 2023 season.
“I would say the last few weeks have been a lot,” Raducanu said.
“I think from the performance today it was very clear that mentally and emotionally I was exhausted.
“I was trying to push through and I was just unable to push through today. I guess the sport is just pretty brutal.”
Raducanu, who dropped to 303rd in the world following wrist and ankle operations last year, was set to play Karolina Pliskova in her opening match – but the former world number one pulled out of the tournament because of a wrist injury.
Currently ranked 221st, Raducanu was unable to recover after falling a double break of serve behind in both sets against her 82nd-ranked opponent.
Harriet Dart was also beaten in straight sets in Madrid.
The27-year-old, who won two qualifying matches to reach the main draw, held a 4-0 lead in her second set against Spain’s Cristina Bucsa but went on to lose 6-4 6-4.
In the men’s draw, Britain’s Jack Draper progressed with a hard-fought three-set win over Australian qualifier Thanasi Kokkinakis.
After Kokkinakis took a tight contest to a decider, the 22-year-old Draper avoided a final-set tie-break by breaking serve in the 12th game to clinch a 6-3 3-6 7-5 victory.
The world number 43 will play Poland’s eighth seed Hubert Hurkacz next.
Elsewhere at the Madrid Open, four-time major champion Naomi Osaka progressed with a comfortable 6-4 6-1 win against Belgium’s Greet Minnen.