Major League Soccer is expanding. This week, a league featuring 20 teams will kick off for the first time, with four more franchises set to be added by 2020.

With two of these slots already presented to Atlanta and a second Los Angeles franchise, and David Beckham’s Miami project seemingly having a priority but no home, the league has at least one space still available. (This could rise to two should Miami’s proposals break down.)

“We remain on track to announce the next MLS expansion market during the first six months of this year,” Dan Courtemanche, the executive vice-president of communications for Major League Soccer, said in an email to the Guardian. “Expansion is conducted very strategically.”

Courtemanche said that when choosing a potential new franchise, the league considers a number of criteria: a committed local ownership group; a stadium plan and ownership of the venue; an appropriate market for sponsors; a history of strong fan support. The likes of TV ratings for MLS games and factors like geographical location are also considered.

“We have all the official parts to have a successful franchise here – it’s just that one party has a team without a stadium, the other party has a stadium without a team,” Joe Leyba, co-founder of MLS4MN, a group advocating for an MLS franchise in the Minneapolis area, said. “I would say that if, within, say, the next three months, the MLS announce a team here, no one will be surprised.”

Orlando City will play in this season’s MLS. Photograph: Nigel Worrall/ Nigel Worrall/Demotix/Corbis

Minneapolis is the only market with two potential bidders though both remain tight-lipped on their plans. One option for the Twin Cities, an area that has the 15th-largest media market in the US, is Minnesota United, a North American Soccer League franchise that refuses to comment on its MLS potential.

“Our ambition, from the first day of our involvement in Minnesota professional soccer, has always been to build one of the greatest clubs in North America and to jealously guard our position as the pinnacle of professional soccer in our market,” Nick Rogers, club president of Minnesota United, said.

Were United to put forward a bid, they would meet many of the MLS’ specifics, Leyba said. The club has a history that stems back to the early 1990s, a loyal fan base and is part of a market that the league have previously expressed an interest in. Reports have also stated that local investment from the Minnesota Twins and Timberwolves’ owners may be available.

The issue for United, Leyba said, would be the construction of a soccer-specific stadium – something the club refuse to comment on, though reports have claimed they are potentially looking at a section of land in the downtown area.

For the area’s other bidders, the NFL’s Minnesota Vikings, a strong stadium proposal is less of a worry. In what would be a similar approach to Atlanta’s new franchise, the Vikings’ bid would see a team play in their new NFL stadium, set to open in 2016. For MLS games, the stadium would be downsized to 25,000 seats. Leyba said that though the stadium would not be an issue, some fans may be torn as to where their loyalties lie: MLS4MN does not side with either bidder, though all of its members are Minnesota United season ticket holders, he said.

“There is only one professional football club in Minnesota, and that is Minnesota United,” Nick Rogers said. “I have no comment on hypothetical football clubs.”

For another bidding city, Sacramento, the hypotheticals seem less of a worry. The area’s professional team, Sacramento Republic, have boomed in popularity since team the MLS’ expansion plans were announced, in 2013, and have set themselves up as strong contenders.

“Sacramento is the most underserved professional sports market in the country,” Warren Smith, president of Sacramento Republic, said. “But, realistically, we have a brand that they [the league] could pick up right away.”

Last season, Republic, who play at USL level, broke league attendance records on their way to winning their first championship. The club are expected to sell more than 9,000 season tickets ahead of the new campaign, while their stadium, Bonney Field (current capacity: between 11,500 and 11,700), has the potential to increase to 14,000 seats.

Though that capacity is less than smallest stadium in the MLS, Smith claims that the club have “very significant commitments that would pay for a stadium – well over $200m.” This capital – some of which is said to be from the Sacramento Kings, the area’s NBA franchise, and the San Francisco 49ers of the NFL – would be used to fund a soccer-specific stadium in the downtown area, which has public support from the likes of the city’s mayor. Sacramento, like Minneapolis, is also a top 25 market, which will appeal to the MLS and potential investors.

“Capital is coward, and it’s always looking for reasons not to invest,” Smith said. “I think that if you have a brand that’s built and has been operating successfully, MLS isn’t going to be taking any risks – it’s easier for them to spend their time, energy and money in that market.”

Smith said that MLS teams with similar backgrounds – “Portland, Seattle, Vancouver, Orlando” – are successful, ground-up clubs that Sacramento hope to emulate. St Louis, however, is a city that will not be taking this route; instead, their approach will be stadium first, team second.

“A lot of people say that it’s unusual that you don’t have an MLS team when the sport means so much to you, but the reason is that we just haven’t had the right venue,” Jim Woodcock, a member of Missouri governor Jay Nixon’s taskforce for bringing a new stadium to the city, said. “Answering that question seems to be more promising today than ever.”

Though MLS have conducted expansion meetings with representatives from Minneapolis, Sacramento and Las Vegas (who are now out of the running), they have also held discussions with representatives from San Antonio and St Louis in recent months.

In a bid to keep its NFL team, the St Louis Rams, the city is currently reviewing proposals for a 60,000-plus-seat, riverfront stadium, which could be completed by 2020. In what would be a private-public partnership, Woodcock’s task force are also looking for alternative uses for the venue – an MLS team, in what would be a similar approach to Atlanta, being one of the preferred options. St Louis, Woodcock said, would appeal to potential investors looking to start a franchise: a soccer-specific stadium would be in place in a market that has a strong history with the sport. For example, in the US’s upset of England at the 1950 World Cup, five of the country’s starting eleven were from St. Louis. The Billikens, Saint Louis University’s men’s soccer team, have won 10 national championships, and the first league in the area, the St Louis Soccer League, began more than a century ago, in 1907.

Facebook Twitter Pinterest US center forward Joe Gaetjens is carried off by cheering fans after his team beat England 1-0 in the World Cup in Belo Horizonte. Photograph: Uncredited/AP

But the biggest problem for St Louis, it seems, is timing. With MLS looking to announce its expansion plans in the coming months, stadium renderings may still be under consideration at that point.

“The NFL has expressed to us that urgency is important,” Woodcock said. “Major League Soccer has a very authentic and sincere interest, so it is in our best interests to move this project along as briskly and responsibly as possible.”

In San Antonio, though, there is a stadium, team, and apparent market for soccer (the upcoming friendly between the US and Mexico, set to be held on 15 April at San Antonio’s Alamodome, is a 65,000 sellout). The local team, the San Antonio Scorpions of the NASL, were founded in 2010, and won that league’s showpiece, the Soccer Bowl, last season.

Scorpions owner Gordon Hartman, who helped bring the team’s privately-owned Toyota Field stadium to the city, admitted that things have moved a lot quicker than he expected, which is why MLS is now being mentioned. The club have had similar discussions to those of St Louis, but, Hartman said, would prefer to keep its updates out of the public eye – for now.

“I am not out here saying, ‘Eventually, someday, we will get there,’” Hartman said. “I want to take the hypotheticals out… I want to say, ‘All these things are in place; we are ready to go. This city is MLS-ready.’”

Hartman said that the club is currently not in a position to discuss potential investors, should San Antonio expand Toyota Field from 8,000 seats to an MLS-standard 18,000 capacity, which the stadium is capable of. Though this would not be a downtown stadium – something MLS prefers – the team have received public support to join MLS, and point to potential rivalries with Dallas and Houston as something that could be attractive to the league.

“We can move very quickly here in San Antonio,” Harman said. “We have checked off all the boxes, and the reason I have continued to do this the way I have is because I want to finalize all the pieces and present that in a complete way to the MLS.”

Over the coming months, the league will continue to assess the prospects of these markets though “no specific date for an expansion announcement has been set,” Dan Courtemanche said.

For the bidders, “we have to be on our toes and be ready to address any issues that come up,” Warren Smith of Sacramento said. “They [the league] have got big things in front of thema new season that they have starting, two new teams… We just have to be patient. It’s not our timeline now, it’s theirs.”