King of the Court

"It was like 'Field of Dreams.' It was like, if you build it, they will come." So he did. The franchise fee was $100,000, and the WTT's Rosie Crews estimates that the annual operating costs for a major market team range from $600,000 to $1 million-plus. That figure includes salaries for those marquee players, who may get up to $75,000 per night.

In came 2,000 tons of concrete to level out the parking lot at 11th and H streets NW. On went the players' draft, in which Serena Williams was tapped to be the Kastles' marquee player.

The stadium is built on the concrete expanse that used to hold the convention center, and then a parking lot, and then an arty parking lot with crushed glass sidewalks and fake grass. It cost $1.3 million; the city kicked in $200,000. As WTT locations go, this spot is apparently a big coup: "I've played in baseball diamonds and cow pastures," says Murphy Jensen, a Tennis Channel host who played on several WTT teams before retiring. "I've played next to the world's fattest pig at a fair. Honestly, this is the best stadium I've ever been to."

Kastles employees (and many summer interns) swarm at every match, ready to be of the slightest assistance, but you get the sense that if Ein could, he would do everything himself.

"He's a big person," says his dad, renowned allergist Daniel Ein.

"He's committed," says his mom, Marion Ein Lewin, who adds that she wishes her son would get married.

"He's passionate," says Fernandez.

Says the Kastles' coach, Thomas Blake, "He's obsessed."

Gets on the court to play with the team every day. Arranged a feature on the Tennis Channel, and tea at the New Zealand Embassy (player Sacha Jones is a Kiwi). Cheers like crazy at every match.

He will make you love World TeamTennis.

"We were just talking," says Ein, in the VIP alley outside the VIP tent on another match night, "about whether there are any consumer businesses where John could get involved."