PARIS—Seventh-ranked Juan Martin del Potro of Argentina has pulled out of the upcoming French Open because of a respiratory virus.

Del Potro was stricken by a virus that affected both his breathing and his stomach at the beginning of the clay-court season. He was forced to pull out of Estoril and Madrid and then returned in Rome, but he came down with bronchitis. Del Potro returned home to Argentina and while his medical team, which is led by Dr. Roberto Peidro, said that he is improving, he has been advised to fully recover before he plays again. The 2009 U.S. Open champion hopes to play at Queen's Club and Wimbledon next month.

"I'm sad to miss such an important tournament, and obviously this is a blow because these are the tournaments that one always dreams of winning,” del Potro said in a statement. “Now I have to get through this time, fully recover and prepare to return at 100 percent.”

American players Brian Baker and Mardy Fish have also pulled out. Baker has not recovered from a right knee operation and Fish is unfit because of heart problems. They will be replaced in Friday's draw by Joao Sousa of Portugal and Guido Pella of Argentina.

U.S. Open champion Andy Murray pulled out Tuesday because of a chronic back injury and will be replaced by a lucky loser.

Also, Australian wild-card entry John Millan withdrew because of a shoulder injury and will be replaced by Nick Kyrgios of Australia.