Monday was the 137th day of the NBA lockout — and it may have been doomsday. The NBA Players Association rejected the latest proposal from team owners on how the league divides its annual revenue. The players also announced that they would end all negotiations, dissolve their union, and file an antitrust lawsuit against the NBA,  claiming that the lockout, which began July 1, is illegal. Here, a guide to the developments, and whether the season is really over:

What's the players' rationale?
The players claim that the league "backed them into the corner with ultimatum after ultimatum," says Zach Lowe at Sports Illustrated. The offer presented by owners on Monday called for a 50-50 split of revenue (a deal many owners believe is too generous to players), and would have allowed for a 72-game season to begin on December 15. But the players, who previously received 57 percent of league revenue, took issue with proposed rules governing contracts and free agency. Owners had threatened that if the players didn't accept the offer on the table, the next one would be even less generous. So, according to union head Billy Hunter, the players "arrived at the conclusion that the collective bargaining process has completely broken down."

So players disbanded their union?
Yes. The move to dissolve the union and become a trade association essentially allows the players to sue the NBA for massive damages. The technical term is a "disclaiming of interest," says Bloomberg. The union's disbanding strips the NBA of antitrust protections that come with the past collective bargaining agreement. With collective bargaining over, the fight over how to divide the revenue moves to the courts.

What could players accomplish in court?
The antitrust suit will seek a judgement that deems the owners' lockout of the players illegal, says Marc Stein at ESPN. If that works, the players would win back in damages the money they've lost by not playing. It's the same tactic taken last summer by the NFL players as that sport faced a lockout, says Bill Ingram at Hoops World. The NBA players are even using the same attorney, Jeffrey Kessler. The NFL lockout ended before the football season started, however. The NBA season was supposed to begin two weeks ago.

And the season might be canceled?
Despite their inability to agree on much of anything else, both sides concede that the latest developments may well spell an end to the 2011-12 NBA season. Because court proceedings will take time, Hunter says there's a "high probability" that the season will have to be canceled. Commissioner David Stern also acknowledged that the season is in jeopardy. "If I were a player," he says. "I would be wondering what Billy Hunter just did." Once a lawsuit is filed, it could take 60 to 120 days for a court to even hear it, says Jeff Zillgitt at USA Today. That means the NBA could be the first North American sports league to lose an entire season since the NHL in 2004-05.

Is there any chance of more negotiations?
"It's not inconceivable" that the two sides might talk again before the NBPA officially files its lawsuit, says Stein. But Stern balked at the notion that the players' move would coax an 11th-hour concession from owners. The players have employed a transparent "negotiation tactic," he said. "But it's not going to work."

Sources: Bloomberg, ESPN, Hoops World, Reuters, Sports Illustrated, USA Today