The remainder of the National Football League season was in jeopardy after negotiations between the striking players and NFL management collapsed today, and mediator Sam Kagel flew home to San Francisco, suspending his 12-day effort to settle the dispute.

NFL Commissioner Pete Rozelle acknowledged today the league might not be able to play out the remainder of the schedule although he would not be specific about when such a decision might be made.

Team owners, he said, "are very concerned. You can't have a fraction of a season and then have postseason tournament games." He said it was not an overstatement to say the season is in "a lot of trouble."

As fans prepared for their fifth consecutive Sunday without NFL football, there appeared to be no end in sight to the 33-day-old strike. No date was set for resumption of the talks.

Jack Donlan, the NFL's chief labor negotiator, said owners will forgo the rest of the season before agreeing to the players' basic demand that a trust fund be set up to pay them on a seniority-based scale with performance incentive bonuses. He said he sees no point in resuming talks until the union changes its basic demand.

But Ed Garvey, executive director of the NFLPA, predicted the owners would return to the bargaining table with a different attitude toward the players' wage scale and trust fund proposal.

Garvey and other union officials will meet Sunday in Washington with player representatives from the NFL's 28 teams to plan further strategy, including establishment of a players' league that would attempt to play an approximation of the NFL schedule if the league cancels the season.

Collapse of the talks today left the two sides little closer to agreement on the basic economic issues in the dispute than they were on Feb. 16 when the initial round of negotiations took place in Miami. The NFL maintains it wants to preserve the system of individual player negotiations that the league has followed since its founding 63 years ago.

"It has been good for the owners. It has not been good for the players," said Gene Upshaw, the NFLPA president. "This strike is about individual bargaining versus collective bargaining."

Kagel, a 73-year-old lawyer and a veteran arbitrator and mediator of labor disputes, announced he was recessing the talks this morning to give the sides time to "reassess and re-examine their positions on very complex economic matters."

He said there had been some progress in the first few days of the mediation, at the Hunt Valley Inn here, and that the noneconomic issues in the dispute had either been resolved or could be resolved.

But Kagel, who was driven to Dulles Airport for his flight back to California by Washington Redskin player representative Mark Murphy, was known to feel the sides were polarized on the basic concept of the wage scale and trust fund and that his mediation was accomplishing nothing on that subject.

It was unclear whether Kagel would continue to participate in the talks if the sides do get back together. Donlan said he assumed he would. But union officials indicated they might prefer to resume bargaining without Kagel.

Murphy said Kagel indicated he definitely "wants to come back into it, but it's something we have to talk about. I'm not sure if he would be effective any more. But it's a matter of getting a fresh face involved who would have to be updated on all the issues. At least Kagel is very familiar with everything now."

Murphy also said he thought the player representatives will continue to support the union's position on its right "to bargain collectively for all our wages."

As they have since the talks began, each side blamed the other for the deadlock.

"We bumped into Ed Garvey's brick wall," said Donlan, describing the union leader's strategy as "a textbook case on how not to negotiate." Donlan also said Kagel told the union "on any number of occasions that their idea for a fund was nonsense."

That statement was heatedly denied by Upshaw.

Garvey noted that William A. Lubbers, the National Labor Relations Board general counsel, has said he will file a complaint accusing the league of bad faith negotiations. Garvey said he plans to ask the NLRB to press for an injunction compeling the league to negotiate in good faith.

Donlan denies the NFL has engaged in any kind of bad faith negotiations.

Collapse of the talks today makes it unlikely that next weekend's games can be played since there would have to be a settlement early in the week for the players to report to practice facilities in time to get ready for the games.

In any event, the NFL now faces a 12- or 13-game schedule -- depending on whether next weekend's games are played. Rozelle has said several owners have said that is the minimum number of games that must be played to preserve the season's credibility.

There are 16 games in the regular NFL schedule and the league says no more than two can be made up -- one by eliminating the postseason wild card game and one in the week before the Super Bowl when no games are scheduled. The Super Bowl, scheduled for Jan. 30, cannot be changed, the NFL says.

But the players union disagrees adamantly. It says the Super Bowl can be changed and says it plans to press for a full 16-game season as part of any settlement.

"There will be a season," said Upshaw. "It might be cold but there will be a season."

Donlan said the executive committee of the NFL Management Council will be meeting within the next few days to decide its options. He said opening practice facilities and attempting to play despite the strike would be one option.