Novak Djokovic was the highest-profile player to complain about the quality of tennis ball at this year's Wimbledon. Many players have speculated that the quality of the ball is factoring into the numerous upsets that have taken place. Alastair Grant/The Associated Press

Highlights of the fourth day at the Wimbledon tennis championships on Thursday (times GMT): 2030 SHELTON ALMOST INTO THIRD ROUND American Ben Shelton needs just one more game to reach the third round after his match with Australian Rinky Hijikata was suspended with the 10th seed 6-2 7-5 5-4 up.