Could the Arena Football League go the way of several other football leagues started alongside or in direct competition to the NFL? Here's a look at the notable leagues, how they fared and where they might have gone wrong.
American Football League (1926)
The Teams: Nine for the first -- and only -- season for the original AFL. The Boston Bulldogs, Brooklyn Horsemen, Chicago Bulls, Cleveland Panthers, Los Angeles Wilson Wildcats, Newark Bears, New York Yankees, Philadelphia Quakers and Rock Island Independents.
The Results: The last game of the season saw the Yankees defeat the Bulls, 7-3, but it wasn't a championship game. The Yankees finished the season 10-5, the second-best win percentage in the league that year, trailing the 8-2 Quakers.
The Stars: Most of the league's publicity came from the Yankees and their headliner, Red Grange. Grange was the league's star, running for five TDs, catching two more, throwing for one and returning an interception for a score.
The Aftermath: While the fans turned out to see the Yankees and Grange, few came to see other teams, and the league folded after one year.
The Legacy: The Rock Island Independents, a charter member of the AFL, were also a charter member of the NFL (then known as the APFA) in 1920.
American Football League (1936-37)
The Teams: The league had six teams in both of its seasons, but the teams varied. Four teams played both seasons: the Boston Shamrocks, New York Yankees, Pittsburgh Americans and Brooklyn (later Rochester) Tigers.
The Results: The Shamrocks ended the 1936 season with the AFL's best record but had their roster gutted by NFL teams and could not replicate their success the next season. The Los Angeles Bulldogs, an independent team the year before, went 8-0 in 1937.
The Stars: The main star power was added to the league's board for the '37 season. Jack Dempsey and Bing Crosby became board members, but the league was already far in decline.
The Aftermath: With rosters gutted by the NFL raids, the second attempt at the AFL failed much like the first one.
The Legacy: The Bulldogs were the main legacy of the second AFL. They were the first to play home games on the West Coast. The Redskins also moved from Boston to Washington before the 1937 season, partially based on the success of the Shamrocks.
American Football League (1940-41)
The Teams: Six teams -- the Boston Bears, Buffalo Indians, Cincinnati Bengals, Columbus Bullies, Milwaukee Chiefs and New York Yankees (later Americans) -- played the 1940 season. Boston disbanded before the 1941 season, and the league continued with five teams.
The Results: Living up to their nickname, the Bullies finished atop the league in both seasons.
The Stars: John Kimbrough, Bob Davis and Nelson Peterson headlined the league.
The Aftermath: Stressing that the league was not in financial trouble, the AFL took the 1942 season off after the attack on Pearl Harbor because many college and professional players went into the armed forces. However, the AFL's third attempt ended up much like the first two.
The Legacy: A double round-robin schedule allowed one team to emerge as a true league champion.
All-America Football Conference (1946-49)
The Teams: Eight teams were on board for the first AAFC season. The Brooklyn Dodgers, Buffalo Bisons (later Bills), Chicago Rockets (later Hornets), Cleveland Browns, Los Angeles Dons, Miami Seahawks, New York Yankees and San Francisco 49ers. The Seahawks moved to Baltimore for 1947 and became the Colts.
The Results: Four seasons, four championships for the Cleveland Browns, who went 47-4-3 under head coach Paul Brown. They might have been too good for the league's good, as their dominance cut down on the competition.
The Stars: Otto Graham made the All-League team in all four seasons as the Browns' quarterback. Spec Sanders had more than 1,400 rushing yards in 1947 for the Yankees, the only back to top even 1,000 yards rushing in the AAFL's history.
The Aftermath: The Dodgers folded after the 1948 season and merged with the Yankees. There were rumors that the Browns would try to play the 1949 NFL champion, the 11-1 Eagles, after they won their fourth straight title, but the game never happened.
The Legacy: Three teams were absorbed by the NFL: the Browns, the 49ers and the Colts, despite the Colts' lack of success. The Colts, not the same franchise that plays today, folded after one NFL season in which they went 1-11.
American Football League (1960-69)
The Teams: Eight teams started the 1960 season in the fourth version of the AFL: the Boston Patriots, Buffalo Bills, Dallas Texans, Denver Broncos, Houston Oilers, Los Angeles Chargers, New York Titans and Oakland Raiders. The Texans moved to Kansas City and became the Chiefs in 1963, and the Titans changed their name to the Jets that same year. The Miami Dolphins were added for the 1966 season, and the Cincinnati Bengals came into the mix for 1968.
The Results: The Oilers won the league's first championship, beating the Chargers 24-16. The game that truly gained notice for the league was the 1962 AFL title game, in which the Texans beat the Oilers in double overtime.
The Stars: A plethora of stars rose to prominence in the offense-heavy AFL, including Joe Namath, Lance Alworth, Jack Kemp, George Blanda, Clem Daniels and Len Dawson.
The Aftermath: The truest competitor to the NFL, the league lost its first two "Super Bowls" to the Green Bay Packers but won the next two with the Jets and Chiefs and was fully merged with the NFL for the 1970 season.
The Legacy: Besides 10 NFL franchises still with the league, the league brought flashiness to football, courtesy of the uniforms and offensive style. Other notable innovations include the two-point conversion, an official scoreboard clock and player names on the back of jerseys.
World Football League (1974-75)
The Teams: Twelve teams started the 1974 season, but several moved around during and after the season. They were the Birmingham Americans, Chicago Fire, Detroit Wheels, Florida Blazers, Hawaiians (Honolulu), Houston Texans (became Shreveport Steamer during the season), Jacksonville Sharks, Memphis Southmen, New York Stars (became Charlotte Hornets during season), Philadelphia Bell, Portland Storm and the Southern California Storm.
The Results: Birmingham beat Florida in the first World Bowl, but had to hand over its equipment because of its debt. It won the 1975 season in even less remarkable fashion, being named champions at the time of the league's folding.
The Stars: The league made some headlines when it signed away three members of the 11-3 Dolphins. Jim Kiick, Larry Csonka and Paul Warfield all got to the league in time to see it fold.
The Aftermath: Teams folded, moved and were renamed after the debut season. Fans still didn't come out. The Chicago franchise folded after just five games in 1975, dropping the league to just 10 teams.
The Legacy: Despite its short stint as a professional sports league, the WFL did have an effect on the NFL. Some of its notable innovations included overtime, moving the goalposts to the back of the end zone, and weeknight games. Not to mention singular team nicknames like the Sun, Storm and Thunder.
United States Football League (1983-85)
The Teams: Nineteen teams in all played in the USFL during its three seasons. The league started with 12 teams in 1983, had 18 in 1984 and dropped to 14 for their final season.
The Results: The 12-6 Michigan Panthers upset the 15-3 Philadelphia Stars for the first league championship. But the Stars came back strong in 1984, going 16-2 and beating the Arizona Wranglers in the title game. Despite the fact that they were the defending champions, the Stars moved to Baltimore for 1985 and dropped to 10-7-1 (fourth in their conference), but still won the championship.
The Stars: This is where the USFL had the best chance to compete with the NFL. The league signed three Heisman winners: Archie Griffin, Herschel Walker and Mike Rozier, along with fellow stars Jim Kelly, Steve Young and Reggie White.
The Aftermath: Before the 1985 season, the USFL announced the league would switch from playing in the spring to the fall in 1986, going head-to-head with the NFL. It also filed an antitrust lawsuit against the NFL. The USFL won the suit but was awarded only $1.
The Legacy: The USFL showed there was a place for another league, given the necessary star power and markets that weren't already tapped by the NFL. The league opened up opportunities for franchises in Arizona and Jacksonville.
Xtreme Football League (2001)
The Teams: The league fielded eight teams for its first and only season: the Birmingham Thunderbolts, Chicago Enforcers, Las Vegas Outlaws, Los Angeles Xtreme, Memphis Maniax, New York/New Jersey Hitmen, Orlando Rage and San Francisco Demons.
The Results: Despite the Rage's having the best regular-season record, 8-2, it was the Xtreme that overcame a missing E, ignored spell check, and beat the Demons in the first and only "Million Dollar Game."
The Stars: Tommy Maddox won the league's only MVP award and went on to have success with the Steelers. The league's biggest star might have been Rod "He Hate Me" Smart.
The Aftermath: Orlando's Hassan Shamsid-Deen's XFL career ended when he separated his shoulder in the opening game's opening scramble, a replacement for the coin toss. The league's demise was even more painful. TV ratings dropped quickly, starting with a 9.5 on NBC. That rating was cut in half the next week and quickly dropped below a 2.0.
The Legacy: Despite the league's becoming little more than a punch line in football history, the XFL had some innovative ideas that are being used by the NFL today. Among their advances were a sky cam, in-game interviews and a college-style overtime.