Serena was taking part in her first match since Wimbledon, whereas Venus has performed singles and doubles at three hard-court occasions in latest weeks.
The pair made a poor begin towards Ukraine’s Kostyuk and American Stearns earlier than shaking off what Serena known as “somewhat rust” within the second set.
They rapidly went down 6-0 within the deciding 10-point tie-break however fought again impressively.
Serena produced two service winners to drive the tie-break again on serve, however Kostyuk and Stearns held agency earlier than securing victory on a double fault from Venus.
“I assumed it was enjoyable, it was particular, it was good,” Serena stated.
“We had been beginning to really feel it. It was actually cool to have the ability to do that once more.”
The sisters would wish wildcards to play both singles or doubles on the US Open, which begins on Sunday, 30 August.
Serena – who described her knee harm as “somewhat traumatic expertise, however what would not kill you makes you stronger” – has solely performed one singles match since her return.
Venus has misplaced her previous 13 singles matches however has had extra success within the doubles, reaching the quarter-finals of the ladies’s match in New York final 12 months.
At their peak, they received 14 Grand Slam doubles titles collectively and three Olympic gold medals.
