Serena Williams' next match: Doubles reunion with sister Venus

Serena Williams will reunite on the tennis court with sister, Venus, to play doubles in the Cincinnati Open this month, a possible hint that Serena will enter the U.S. Open later in August.

Williams, 44, ended a four-year retirement and made her comeback to professional tennis in June at the HSBC Championships in London, winning a doubles match partnered with Victoria Mboko. Williams then entered Wimbledon as a singles wild card and lost in the first round. She was supposed to play doubles at Wimbledon with her sister, but was forced to withdraw due to a knee injury that cast doubt over her status for the U.S. Open.