Roger Federer and Novak Djokovic call for rule change as rivals wave white flag

Roger Federer and Novak Djokovic have called for Wimbledon to change its rules after both of their opponents retired on a disgruntled Centre Court.

Djokovic was leading Martin Klizan 6-3 2-0 when the Slovakian succumbed to a calf injury before Alexandr Dolgopolov pulled the plug in his first-round match at 6-3 3-0 down to Federer.

Klizan and Dolgopolov were two of seven men to withdraw during their first-round matches, with Viktor Troicki and Janko Tipsarevic both spending less than 20 minutes on court.