The Washington Kastles open their sixth season Monday night as the two-time defending World TeamTennis champions seeking their 33rd consecutive victory. But elbowing into the crowded hearts and schedules of D.C. sports fans is difficult, and while the Kastles have a devoted fan base, those marketing the team and its league have to answer one question for the average sports fan: Why team tennis?

Jason Spitz, vice president of marketing for the league, said the league is trying to “appeal to a broader sports fan” by emphasizing the part of its tennis product fans can’t find on the mainstream tours: the team.

 World TeamTennis “puts a new spin on what is out there,” Spitz said. “We’re supplying tennis content but we’re appealing to the broader sports fan through the concept of team, and that’s attractive to a lot of our partners.”

The league is entering its 38th season and has a broadcast deal with the NBC Sports Network, signs of success despite its limited national visibility. As league chief executive Ilana Kloss put it, “I don’t think we would have lasted this long if we weren’t profitable.”

World TeamTennis is an eight-team league founded in 1974 by tennis legend Billie Jean King to allow men and women to compete together and create a team-first environment more attractive to fans of traditional team sports. Music plays between points, on-court entertainment abounds between matches, and fans are allowed — in fact, encouraged — to root with football-ready vehemence, rather than the more reserved tennis etiquette.

 Each match consists of a set each of men’s singles, women’s singles, men’s doubles, women’s doubles and mixed doubles, all played to six games. Competitors don’t have to win by two points, and each individual game of a set counts toward the team score. That setup creates a fast-paced, high-energy game that more closely resembles the rooting experience of U.S. major team sports than a day at Wimbledon.Rosters typically feature up-and-coming youngsters, middle-of-the-tour veterans and a featured star (the Kastles will feature Martina Hingis in their opener).

According to Kastles player Bobby Reynolds, the league’s male MVP of the 2012 season, the format allows fans to get to know players and develop a rooting interest similar to with a football or baseball team, but not in traditional tennis.

“Most of the time if you see it on TV or you go to a match, it’s one person versus an opponent and you don’t really get to know each player individually . . . with Team Tennis, there’s so much fan interaction with the players.” Reynolds said. “I’m interacting off the court, on the court, when I’m sitting on the bench.”

Those fans often get a sneak preview at the next generation of stars.

In 2000, a 17-year-old up-and-comer with a power game headed to Boise, Idaho, to play with the now-defunct Idaho Sneakers. Three years later, that player, Andy Roddick, won the U.S. Open.

Now a part owner of WTT along with Venus Williams, Roddick said he wants to both give back to the league that he said served as a “springboard” for his career and build popularity for a sport that’s beloved globally, but is often placed on the back burner in the team-centric minds of American sports fans.

“All the things that are applied to tennis as stigma — that it’s not accessible, that it’s a country club sport — [WTT] goes the other way.” Roddick said. “. . . I think it has a really good place in the tennis world.”