After playing downtown in a temporary stadium last year, the Kastles home venue, which features a unique multi-colored court, now is on the Potomac River. And it has been filled to capacity for all of their games this season.

At one match, even first lady Michelle Obama and her two daughters came out to cheer the home team.

World Team Tennis features men and women in singles, doubles and mixed doubles, and has its own scoring rules and regulations.

Venus Williams likes that aspect of the league.

“Every game counts, so even if you don’t win your match, if you get some games for your team, ultimately that can lead to a win for everyone. So everyone has to contribute an equal part, and that’s what really makes it unique,” she said.

Serena Williams said she enjoys being her older sister's teammate.

“She doesn’t necessarily give me advice. We just go out and do our best and try to play well for the Kastles. We’re both really excited to be playing for the same team,” said Serena.

And the Washington Kastles, which also features doubles specialist Leander Paes of India, has been the best this season in World Team Tennis, becoming the first team to clinch a playoff berth by winning their first 13 matches.