The world No. 1 and the world No. 3 are both in action on Wednesday, as are the Williams sisters.
Venus, 39, won four grand slam titles before Coco Gauff, 15, was born. Venus had trouble dealing with Gauff's serve on Monday.
Twitter users accused the men of "repulsive racism" and branded their actions "disgusting."
Venus Williams, Sloane Stephens and Coco Vandeweghe lost.
Age and experience have been key this year in SW19.
Murray begins his defense on Monday in London.
The tennis star was involved in a car crash that killed a man in early June.
Williams won her 23rd Grand Slam singles title at the Australian Open in January, when she was already close to two months pregnant.
Four all-time tennis greats will clash this weekend in the Australian Open finals.
The sisters last contested the Wimbledon 2009 final.
Alleged Russian hackers have released confidential data of U.S. and U.K. athletes, including Bradley Wiggins and Venus and Serena Williams.
The world number two is within touching distance of a second Wimbledon title.
The world No. 1 was responding to comments by tournament director Raymond Moore.
Victory over Zhang Shuai sent Britain's top-ranked female player into the Australian Open semi-finals.
The multiple Grand Slam winner failed to turn up to a press conference after the defeat.
Serena Williams will face off against Roberta Vinci of Italy at 11 a.m. ET on Friday.
On Tuesday evening, Serena defeated Venus and Djokovic prevailed against Lopez to advance.
The quarterfinals begin without Andy Murray, who exited the tournament in an upset Monday.
As the tournament enters its second week, temperatures remain high and the stakes get higher.