During the match, which the sisters insisted was an adventure rather than an ordeal, their mother, Brandy, sat in a neutral corner, smiling and fanning herself with her grounds pass.

According to her, it mattered less which sister won the match than how they would treat one another after it was over.

When Serena offered her sister a rather dejected handshake after conceding the match with a netted backhand, Venus immediately put a conciliatory arm around her shoulders and held tight.

Then the two joined hands for a shared bow, evidently the first of many.

“What you saw was something for the future,” Serena said.

The sisters were smiling, sort of, and baring their orthodontia a tad uneasily as they met at the net of the sun-dappled stadium court before their first meeting as professionals. The last time the siblings squared off was eight years ago, when Serena, then 8, got all the way to the final of her first junior tournament only to find herself swatted into submission by her big sister, 6-2, 6-2.

Serena Williams said this was a match that held no fear factor for her, and in the opening set she was her own worst enemy. She compromised herself from the service line with seven double faults and blasted a forehand way wide of the sideline at set point. She had a lead throughout the tiebreaker until Venus scooted in front, 5-4, thanks to a backhand blunder from the youngest but burliest Williams.

Both sisters were more proficient with their returns than with their serves in the first set, when they shared eight service breaks in 12 games. But in the second set, Serena, who wore green beads in her coif in honor of the Green Bay Packers and read some “Hamlet” to put herself in the mood for this intrafamily intrigue, was the sister who cracked first.