With 20,000 seats, Audi Field opened last summer in Southwest D.C. (Ricky Carioti/The Washington Post)

It is naive to think that stadiums, particularly new ones, will serve one team and one sport only. Financial reality obliterates that fantasy. Even the holy grounds of Yankee Stadium and Fenway Park have opened their gates for activities beyond baseball.

In the lobbying, planning and construction phases of Audi Field, D.C. United officials said repeatedly that the 20,000-seat venue would welcome much more than MLS matches. After spending up to $250 million of their own money, and $150 million of the city’s, club investors were not going to limit the stadium’s use to 20-25 soccer matches per year.

Even so, it was a jolt to many supporters recently to hear that the reincarnated XFL would inhabit the Southwest D.C. facility, starting in 2020.

Football, played by men much larger and more violent than soccer players, takes a toll on grass surfaces — fields that need to meet high standards to facilitate quality soccer, which, at its best, is conducted on the ground.

The time of the year is troublesome: With the XFL planning to operate between February and May, the field might become vulnerable to the transition from winter to spring (think snow, ice, mush and temperature swings).

The MLS season commences in early March.

United officials are, as one person close to the team said, “hyper-aware of the effects on the field.”

Contract details were not disclosed, but United has apparently included clauses that require the XFL to pay for major field repairs and possible resodding. Additionally, United matches have scheduling priority and the teams will not host games in the same week.

Each XFL team will play a 10-game schedule, meaning just five home dates, plus possible playoffs.

Jason Levien, United’s co-chairman and chief executive, said he did not want to comment.

United, which opened Audi Field last summer, is among three MLS teams that will share facilities with the XFL. The Seattle Sounders and Los Angeles Galaxy are the others.

Seattle’s CenturyLink Field, which is already home to the NFL’s Seattle Seahawks, has artificial turf and won’t be as affected as Audi Field and StubHub Center, the Galaxy’s grass-covered venue. (StubHub Center also took in the NFL’s Los Angeles Chargers last year.)

Houston’s BBVA Compass Stadium is used by both MLS’s Dynamo and Texas Southern University football (five games in the fall). The New England Revolution shares Gillette Stadium (artificial turf) with the NFL’s Patriots. New York City FC co-exists on grass with the Yankees during long, concurrent seasons.

Mercedes-Benz Stadium (turf) is used by Atlanta United and the Falcons. Vancouver’s BC Place (turf) houses MLS’s Whitecaps and the CFL’s Lions. Toronto FC and the CFL’s Argonauts occupy BMO Field (grass).

United is aiming to stage 50 to 75 on-field events (sports and concerts) annually at Audi Field and some 200 overall (corporate and family gatherings in the indoor areas, for instance).

So what else is coming to Audi Field? The team, sources said, is looking to host rugby and lacrosse next year. Conversations have taken place with two lacrosse circuits: Major League Lacrosse and Premier Lacrosse League.

The organization is interested in staging MLL’s championship game in September, if it doesn’t conflict with a United match. The 2019 MLS schedule is in the preliminary planning phase and should be finalized in a few weeks.

This year, MLL played the final at a United Soccer League stadium in Charleston, S.C. Founded in 1999, MLL has nine teams, mostly on the East Coast.

An MLL spokeswoman said the league is “still considering a number of venues” for the 2019 final. “Audi is a fantastic venue and space.”

The other lacrosse league will debut in 2019 and, instead of playing traditional home games, will tour 12 markets.

It is unclear which rugby events United is targeting.

Meantime, Audi Field has already missed out on supplementary soccer opportunities. The Concacaf Gold Cup, a biennial tournament that will be held again next summer, selected mid-sized MLS stadiums in the Los Angeles, New York, Kansas City, Dallas, Houston and St. Paul-Minneapolis areas, but not Washington. (Several NFL venues were chosen, as well.)

One major issue: Audi Field is equipped with three locker rooms instead of four, which is required for doubleheaders. All Gold Cup group-stage dates and quarterfinal round are doubleheaders.

Audi Field was also passed over for a tour by the U.S. women’s national team leading to the Women’s World Cup next summer. The top-ranked Americans will play at MLS stadiums in the Philadelphia, Denver, Los Angeles and New York areas. (They’ll also appear at NFL stadiums in Tampa, Nashville and Santa Clara, Calif., and the baseball park in St. Louis.)

Audi Field could, however, end up welcoming the women’s team as part of a post-World Cup tour.

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