Third-seeded Mats Wilander of Sweden, weakened by stomach problems, lost to Paul Annacone in the Queens Club grass-court tennis championships Friday in London.
"I did not feel good from the beginning," said Wilander, who was defeated, 6-2, 6-4. "It is just something that is going around and started in the morning. I just didn't feel up to it."
Annacone, who will face top-seeded Ivan Lendl in the semifinals, took advantage of the situation, attacking often.
Lendl was also pressed but had enough left to beat Michael Stich of West Germany, 6-4, 4-6, 6-3.
Others advancing to the semifinals were Derrick Rostagno, who turned back Gary Muller of South Africa, 6-7 (9-7), 6-2, 6-2, and Christo van Rensburg of South Africa, who downed Chris Bailey of Britain, 6-2, 6-4.
Martina Navratilova advanced to a semifinal match against Elna Reinach of South Africa in a tournament at Edgbaston, England.
Navratilova was almost invincible on her own serve, giving up only seven points in a 6-4, 6-2 victory over Australian qualifier Kristine Radford.