While battles over union rights make headlines in Wisconsin, a different kind of labor dispute threatens to derail America's most popular sport. The National Football League is in the midst of a showdown between players and owners that threatens to shut down the league for the first time since a players' strike in 1987, and deprive millions of Americans of their beloved Sunday games this fall. Here, a guide to the high-stakes dispute.

What are players and owners arguing about?
The owners and the players union must renew their collective-bargaining agreement, which was agreed to in 2006, and expires this year. The NFL, a financial juggernaut, makes $9 billion a year through ticket sales, corporate sponsors, and broadcast deals. The two sides must agree on how to split the money.

What do the owners want?
Currently, the owners take $1 billion off the top before dividing the rest. Last season, the players got almost 60 percent of the remaining $8 billion. Owners would like to increase that initial takeaway to $2 billion, which would reduce players' overall share of the pie from about $4.8 billion to about $4.2 billion. Owners also want to extend the NFL's regular season from 16 to 18 games, and cut pay for rookies.

What do the players want?
Given the recent spate of former players suffering from concussion-related brain damage, players argue that adding more games, and increasing the risk of injury, would be irresponsible. Players are also against any pay cuts. They stress that even though NFL superstars make millions of dollars per season, the median salary is only $790,000 — and the average player is in the league for fewer than four seasons, hardly guaranteeing lifelong financial stability.

Where do the negotiations stand?
Owners walked out of the talks in February after they balked at the players' proposed deal. Weeks later, the sides agreed to try again. Negotiations were set to expire last Thursday, but the deadline was pushed back to this Friday, March 11. Some see the continuation of talks as a hopeful sign that the framework of a deal is imminent. One thing is clear, says Howard Fendrich at Yahoo!: By "buying extra time, the league and union made it clear neither was quite ready to make the drastic move of shutting down a league that rakes in $9 billion a year and is more popular than ever."

What happens if the talks fail?
The owners could lock out the players, leading first to the cancellation of spring practices, then to the loss of games in the 2011 season. Players would almost certainly move to decertify their union, which would allow them to seek an injunction in court, which could prevent the owners from shutting down the league. If that happens, the next phase in the war would likely be a series of long, drawn-out court battles. In court, "the players would have the edge, to be sure," says Peter King at Sports Illustrated. But the NFL "would appeal every verdict," and weeks and months would go by, with millions of dollars going down the drain.

What are the chances this will be resolved?
Both sides have maintained a policy of not speaking with the media about any developments, or lack thereof, during negotiations, so it's difficult for outsiders to track progress. But with the pressure on — even the president has weighed in to implore players and owners to reach a deal — the NFL will be disappointing a huge number of fans if it doesn't produce some kind of agreement. And with its public argument about big money in the midst of an economic crisis, the league is already leaving some fans disillusioned: "Enough already," says Paul Newberry in the Associated Press. "This is NOT the time for the billionaires (a.k.a. the owners) to draw a line in the sand against the millionaires (a.k.a. the players)."

Sources: New York Times, Wall St. Journal, Sports Illustrated, CNN, AP