Elena Baltacha lasted only seven games of her opening match at the AEGON Classic in Birmingham on Wednesday, but Anne Keothavong reached the second round with a battling performance.
British number one Baltacha continued her good form in 2010 by winning the ITF title in Nottingham last week but it came at a cost as she was laid low by heatstroke.
Baltacha admitted earlier in the week she was struggling to recover and she called it a day after losing the first set 6-1 to Estonia's Kaia Kanepi.
"I didn't feel too bad in the warm-up but I felt terrible by 2-1," said the Scot. "I felt sick. I got the trainer and the doctor on and they gave me some pills but they didn't really help.
"I wanted to try to battle on but it was just dragging me down. My preparation wasn't great and I ended up spending a couple of days in bed before coming here.
"Now I want to be fully fit for Eastbourne (next week) and give it a good pop there."
Keothavong was given a major test by France's Pauline Parmentier before coming through 4-6 7-5 7-5.
The Londoner was a break down in the deciding set but pulled through and is now scheduled to meet top seed Li Na today.
The sixth and the eighth seeds both exited the tournament at the second-round stage.
Yaroslava Shvedova, a quarter-finalist at the French Open, lost 6-4 6-4 to qualifier Sesil Karatantcheva, while Anna Chakvetadze was a 6-4 6-4 winner over Andrea Petkovic.
There were few problems for number five seed Sara Errani, who beat Shenay Perry 6-2 4-6 6-1, while Magdalena Rybarikova, Angelique Kerber and Alla Kudryavtseva all reached round three.
In other first-round matches, Karolina Sprem defeated Kristina Barrois 5-7 7-6 (7/5) 7-6 (7/4) and Jill Craybas saw off Sophie Ferguson 7-5 4-6 7-6 (7/3).