Major League Baseball

• Open markets: MLB has few options. Only two open markets in North America have sufficient income bases to adequately support new teams, and one of them (Montreal) lost a franchise to Washington five years ago.

• Existing markets: Thirteen MLB teams play in 12 metropolitan areas that are currently overextended. (The San-Francisco-Oakland market has two teams.)

• Scenario: MLB couldn’t expand by more than two teams. The best bets would be New Jersey (part of the New York City market, which already has two franchises) and Southern California (San Bernardino-Riverside).

National Football League

• Open markets: Eighteen open markets have sufficient economic capacity to add NFL franchises. The obvious choice is Los Angeles, but there are several other intriguing candidates, including Birmingham, Honolulu, and Las Vegas.

• Existing markets: Eighteen NFL teams are located in 17 overextended markets. (San Francisco-Oakland again is represented twice.)

• Scenario: The sky’s the limit, given the current popularity of pro football. Putting one expansion team in Los Angeles is a no-brainer; as many as five other cities could be picked. Why not add Montreal and Sacramento to the list?

National Basketball Association

• Open markets: Seventeen markets outside the NBA have income bases that are large enough to support teams. Louisville and Virginia Beach-Norfolk have had pro basketball in the past, and Las Vegas is an interesting possibility.

• Existing markets: Competition is especially fierce in the 11 NBA markets that are overextended.

• Scenario: Expansion by four teams would be feasible. Good choices might be Louisville, Virginia Beach-Norfolk, Las Vegas, and perhaps Seattle. The latter would replace the SuperSonics, who moved to Oklahoma City last season.

National Hockey League

• Open markets: Hockey has its pick of 16 open markets, but there’s a catch. Many of the best prospects, notably Houston and Las Vegas, are Sunbelt metros. And the NHL already has its share of troubled Southern franchises.

• Existing markets: Nine NHL teams are shoehorned into markets that are already overextended.

• Scenario: Hartford and Portland, Oregon, seem the best U.S. options for NHL teams. Three Canadian metros (Hamilton, Quebec City, and Winnipeg) are below the income threshold, but could thrive on intense passion and regional marketing.

Major League Soccer

• Open markets: Where couldn’t MLS go? Soccer is by far the cheapest of the five major sports to support. Forty-two open markets have enough money to join the league, but how many would be interested?

• Existing markets: There’s good news here. Just three current MLS franchises are in overextended markets, the lowest number of any league.

• Scenario: New MLS teams are coming on line in Philadelphia, Portland, Oregon, and Vancouver in the next two years. Future possibilities include several markets with demonstrated soccer interest, such as Montreal and Rochester, New York.