Kim Clijsters withdrew from the Unicef Open with a stomach muscle strain Friday, saying she did not want to jeopardize playing in her last Wimbledon before retirement.
Clijsters' physiotherapist, Sam Versleghers, said the 29-year-old Belgian felt the injury a day earlier in her tough two-set quarterfinal against Francesca Schiavone. The announcement came just hours before Clijsters was due to play Urszula Radwanska in the semifinals.
"This is a decision taken with my head, not my heart," Clijsters said in a statement. "But preventatively withdrawing from this tournament is the right decision. I am definitely going to play at Wimbledon."
The four-time Grand Slam winner is unseeded at Wimbledon for the first time since 2000 and has a tough first-round draw against 18th-seeded Jelena Jankovic of Serbia.
Clijsters said earlier this year she intended to retire after the U.S. Open, where she won in 2005, 2009 and 2010. She also won the Australian Open in 2011.
On court Friday, Philipp Petzschner of Germany beat Xavier Malisse 7-5, 7-5 to reach the final. Top-seeded David Ferrer was playing Benoit Paire of France in the other semifinal.
Kirsten Flipkens beat Roberta Vinci of Italy 6-4, 7-6 (5) in a quarterfinal halted by rain Thursday night. Flipkens was playing Nadia Petrova in the semifinals later Friday, while Radwanska advanced to the final because of Clijsters' withdrawal.