TENNIS: Serena fighting to be fit for Wimbledon doubles with Venus after knee issue

Serena Williams will do everything to be ready for her Wimbledon doubles campaign alongside older sister Venus after sustaining a knee injury during her opening singles defeat on Tuesday, the American's agent said.

The 44-year-old's highly anticipated comeback to competitive action after four years away ended in disappointment after a 6-3 6-7(6) 6-3 defeat to little-known Australian Maya Joint, and she later skipped her mandatory post-match press conference.

British media reported the 23-times Grand Slam champion was not fined for her absence because she was injured, with the focus now shifting to her doubles commitments this week after she received a wild card to compete with Venus.

The Williams sisters are drawn to play Solana Sierra and Camila Osorio in the opening round.

"Serena tweaked her right knee at the end of the first set (against Joint) and was excused from her media obligations by the Wimbledon and WTA medical teams," Williams' agent Jill Smoller was quoted as saying in the Times newspaper.

"She left site that night unaided and is doing everything she can to be ready for her doubles match later this week."

Williams has had a little more time on court in doubles action after partnering Canadian teenager Victoria Mboko at the WTA event at Queen's Club last month. The pair's campaign was cut short after Mboko's knee injury in singles action.

Williams then paired up with Czech Karolina Muchova in the Berlin Open but the duo went down in their first match.

-Reporting by Shrivathsa Sridhar in London; Editing by Alison Williams/Reuters