At first glance, Assembly Square and Gillette Stadium during a New England Revolution game present one striking similarity: the two sprawling landscapes are mostly vacant.

The difference, besides the fact one is a development site rife with potential and the other a 68,000-seat stadium better known for its owner’s more popular team (maybe you’ve heard of the New England Patriots), is this: one of them is filling.

After 15 years of dealing, planning and plenty of arguing – oh yes, let’s not forget the arguing – buildings are going up at Assembly Square. A train station is being built. Space is being leased. And for the most part the people who did all that arguing over the last however-many years are happy.

But over in Foxborough, things have become stagnant in recent years for the Revolution. The team is one of Major League Soccer’s original 10 clubs and advanced to four Major League Soccer Cup Finals in the 2000s. But the team currently finishing up their third consecutive losing season. Home attendance in 2012 sits at second to last in the league, with an average of 13,281 people attending each game.

Interviews with Somerville Mayor Joseph Curtatone and Revolution President Brian Bilello, as well as reports from other media outlets, reveal that Assembly Square and the Revolution could be on a collision course. The Krafts and the City are exploring the possibility building a 20,000- to 25,000-seat soccer-specific stadium in Assembly Square. The likelihood of that happening and the extent to which it would benefit the city remain unclear.

A lot of empty seats

From a soccer standpoint, the Revolution needs a stadium to call its own. One in Boston’s urban core, with easy access to the MBTA. You can’t get to Foxborough on the commuter rail, except during Patriots games. And the types of fans that represent a goldmine for MLS – young people who grew up with soccer in the United States and immigrants who grew up with it elsewhere – live in the city and many do not have cars. For these potential fans, the trip out to Foxborough isn’t just unattractive. It’s not very doable.

Though the team’s attendance numbers this year represents a slim upgrade from last year, the 0.44 percent increase trails league-wide growth of almost 7 percent. But beyond attendance issues, playing at Gillette has a negative cultural effect on the team and its fans as well.

The stadium is property of the Kraft Sports Group, which also owns the Patriots and the Revolution. Though it easily fills nearly 70,000 seats for Patriots games, those Revolution fans that show up to watch soccer amount to a drop in a bucket. Soccer fans’ support often manifests itself in song, and the Revolution supporter groups are always eager to flex their vocal cords. But with a crowd that doesn’t even fill a quarter of its seats, those songs have a hard time filling a stadium so big.

Revolution fans even go so far as to theorize that the reason NBC Sports has not shown a game in Foxborough on its weekly national MLS broadcast is out of embarrassment for the emptiness of the stadium. Fans aren’t happy that the Revolution, once one of the league’s flagship franchises, is one of just five MLS teams to not play in a soccer-specific stadium. “At what point,” asks Revolution fan Steven Stoehr, who blogs at The Bent Musket, “does it stop being worth it to abuse your fans like that?”

With some regularity, the team gives the fans hope that a stadium is coming. But want to know another Revolution fan theory? Here it is: the rumor of a stadium briefly surfaces almost every autumn, right around the time the club begins to court season ticket holders to renew. Still, Stoehr said, from a fan perspective, there may be reason for optimism this fall. “This story has picked up steam this time around and stayed important,” he said, noting this year’s round of stadium news surfaced on Sept. 20 and has lasted almost month.

But as much as the Revolution needs a stadium from a soccer perspective, they don’t necessarily need it from a business perspective. Gillette already belongs to the Krafts. Ticket sales could be higher elsewhere, but a ticket sold in Foxborough is revenue all the same, and it comes without the cost of new construction.

A lot of open space

The idea that the Revolution could come to Somerville isn’t a new one. Word first broke on the possibility in 2007, when the Revs were competing for league championships. At that time, the Inner Belt/Brickbottom area was more regularly mentioned than Assembly as a potential stadium site. The neighborhood was projected to eventually serve as the site of a Green Line extension and featured plenty of developable land. Because it stood behind Assembly in terms of development planning, a stadium would help establish the neighborhood’s basic infrastructure when redeveloped – both physically and economically.

The recession stalled the talks between the club and the city, while also violently shoving back the due date of the Green Line Extension – originally expected to be open by now and currently expected to open, best case scenario, by 2018. Through the recession, Assembly development sat still before development started moving forward earlier this year. With the Green Line’s arrival in the Inner Belt and Brickbottom still questionable, it’s unlikely any stadium talks would focus on the area this time around.

In July, IKEA announced it would not be opening a store in Assembly Square – a decision that had been widely expected in Somerville since 2006 when the Swedish furniture giant opened a Stoughton store. With more than 5 million square feet in space suddenly opened up, buried deep in message board threads on soccer websites, Revolution fans began wondering again if Somerville could be a possibility with all that room suddenly available.

Curtatone has repeatedly said since even before the decision was announced that should IKEA opt not to open a store, the site would not play host to development at the same scale as the retail outlet. And with IKEA currently “quietly shopping” the land, according to Curtatone, it bears mentioning that there is other vacant land in Somerville’s newest neighborhood.

There has been little said publicly in recent years about the land in Assembly controlled by RD Management. Currently, a vacant AMC Theater and a swath of parking define the space, which sits between the office building at 5 Middlesex Ave. and the Assembly Square Marketplace. Based on similar stadium projects, the land is not big enough to play host to a 20,000-seat stadium and a parking lot, but it could contain the stadium and some parking while sharing parking with the Marketplace. (The IKEA land is conceivably large enough for a stadium, parking and more.) If a stadium were to go into Assembly, this land would put it further than the IKEA site from residential developments set for Assembly Row.

Asked if the organization was considering land in Assembly for a stadium other than IKEA, Revolution President Brian Bilello said the team would follow the directives of the City if it were to make a deal with Somerville. Posed with the same question, Curtatone said, “Absolutely.”

Where’s the money?

Neither Bilello nor Curtatone could offer any specifics about a financing model, with both parties saying all talks to this point have been preliminary. City Hall did provide what appear to be preliminary notes, comparing financing models of other MLS stadiums across the continent. The models differ widely, from completely publicly-funded to completely private projects. Most of the models involve public-private partnerships – incidentally, a favorite Curtatone phrase – and range between $100 million to $150 million in cost.

Curtatone repeatedly said that any project would need to be in the best interests of Somerville. “We’re not going to do anything to threaten our best-in-history credit rating,” Curtatone said. City spokesman Tom Champion clarified the remarks, suggesting that should the City put public money toward the project it would expect some level of participation in the stadium’s revenue stream at least until its stakes in the project were paid back.

For some, breaking even would not be enough. The city and developers fought with activist group the Mystic View Task Force for a big chunk of the 2000s about the future of Assembly. By the end, the parties reached an understanding. The activists were pleased to eventually reach an agreement that called for 5 million square feet of office and research and development space. Never fans of IKEA’s presence on the site, MVTF members hope the land will now be used for more high-value, tax revenue-generating development. And the space that belongs to RD is slated for office and retail space.

To opt for a stadium at either space could incite the group anew. Indeed, Bill Shelton – a Mystic View Task Force member (and occasional Scout columnist) – wrote in an email, “A soccer stadium would squander the site’s potential to create jobs and tax revenues, while discouraging more productive uses of the land surrounding it. This could be the first test as to whether city officials will faithfully implement the new comprehensive plan.”

A stadium would not generate the same sorts of property tax revenues or jobs as high-end densely-packed office buildings but it would present a major draw to the neighborhood and the city, not just for Revolution games but for other sporting events, concerts and more. Whether a stadium’s effect on commerce strong enough to justify its presence would figure to be a point of contention between the City and activists if a deal with the Krafts were struck.

Keeping score

Somerville is not alone in seeking to host the Revolution. Alongside Revere, the city does appear to be one of two finalists.

On Sept. 20, The Revere Journal reported the team was in discussions with Revere about building at the Wonderland racetrack, right off the Blue Line. The Boston Globe followed with its own report on Oct. 1. The gist: Suffolk Downs, which owns the 34-acre Wonderland, is expected to become the site of a casino for the Greater Boston region. If and when the project is approved, as written in the casino legislation passed in the State House last year, the City of Revere will get to make mitigation demands of Suffolk Downs – which can include cash. Revere Mayor Dan Rizzo would use that leverage to acquire Wonderland and turn it into a stadium for the Revolution.

Put simply, fewer public resources – the amount would depend on the kind of deal Rizzo could work out – would be used to secure the MBTA-accessible Revere site.

Fall River also recently joined the fray. While Fall River is expected to eventually host a commuter rail station, the city lies well outside Greater Boston – which would appear counter-intuitive to most of the Revolution’s public comments to date.

The Krafts might value Fall River’s participation if only to further leverage Somerville or Revere. Revere’s own participation has already had an effect on Curtatone’s rhetoric.

I first talked to Curtatone about a stadium on Sept. 29, when he confirmed the City and the Krafts had been talking for several months. He spoke about as loosely as you might expect a politician to about a major business deal – not very – but his tone and message were hopeful. Though he stressed that any deal would have to benefit the city, his common refrain was that Somerville and Assembly Square would make a great fit for the soccer team.

The Globe story about Revere ran two days later. Champion called me to set up a second chat with Curtatone, and when we touched base, the tone had changed: though Assembly would still make a good fit, he said, the more common refrain was that the City was “not going to get into a bidding war.”

That week, Curtatone and Champion would appear across regional media in stories by New England Soccer Today, The Boston Business Journal and The Somerville Journal about the possibility of a stadium, offering those more measured sentiments. Meanwhile, Rizzo took to the media on his own, going on FOX25 News and saying: “I view Revere as soccer central.”

That won over some fans, the Revolution blogger Stoehr said. “It’s so validating to hear something like that. They’re basically begging us to come. As a fan, you can’t beat that…Somerville seems to just offer canned statements, saying, ‘Don’t forget about us.’”

But then, Curtatone would likely defer to Revere the enthusiasm edge. His administration’s primary talking point has remained the same since the Revere news broke into major media outlets. “If a stadium deal takes away resources from any of our priorities, then we’re not interested,” he told The Boston Business Journal. “It’s important to note that large-scale, smart-growth, mixed-use development is already well under way at Assembly Square: a stadium is not an essential component in the City’s development strategy for the district,” Champion told The Somerville Journal.

At least publicly, Somerville’s enthusiasm is not as strong as Revere’s – but neither are its resources, provided the casino becomes approved and Revere acquires Wonderland.