From BBC Sports http://news.bbc.co.uk/sport1/hi/tennis/6258710.stm
Injured Haas out of Federer match
Haas's withdrawal means Federer will get a bye into the quarter-finals
Tommy Haas has been forced to pull out of his fourth-round Wimbledon singles match against Roger Federer because of a stomach injury.
The German 13th seed was due to face the reigning champion on Centre Court on Monday, but Federer will now earn a bye into the quarter-finals.
Haas sustained a torn muscle in his third-round win over Dmitry Tursunov.
Federer will face 2003 French Open champion Juan Carlos Ferrero or Janko Tipsarevic in the last eight.