Defending champion Venus Williams progressed to the quarter-finals of Wimbledon when Ana Ivanovic quit their match due to injury.

Williams had looked every inch the title holder as she swept through the first set 6-1, her only moments of concern coming in the first game in which she had to save three break points.

It was the 30th consecutive set Williams had won at Wimbledon, the third seed having not dropped a set since her third-round match in 2007 against Akiko Morigami.

However, Ivanovic appeared to suffer an injury to her left thigh while serving in the opening game of the second set.

The 13th seed had her left thigh taped up but was clearly hampered and, although she went on to win the game, she retired in tears at the change of ends.

Williams goes through to meet Polish 11th seed Agnieszka Radwanska in the last eight.