Melbourne: Four-time champions the Williams sisters pulled out of the Australian Open doubles on Friday after an injury to elder sister Venus.
The American pair withdrew from their first-round match with Kristina Mladenovic and Flavia Pennetta because of the injury to Venus's lower left leg.
Serena Williams, seeking her sixth singles title in Melbourne, said she hoped to be back next year playing doubles with Venus. The extent of the injury was not known.
"Well, I love playing doubles, love playing with Venus, but sometimes it doesn't work out," said Serena after beating Daniela Hantuchova in the singles third round.
"We'll make sure we come back and play maybe next year."
Venus, who reached the final of this month's Auckland Open, crashed out in the first round of the singles against Russia's Ekaterina Makarova.