Negotiators for the National Football League and the striking NFL Players Association will return to the bargaining table Saturday in New York in what may be a last-ditch effort to salvage the season.

Mediator Sam Kagel, who broke off talks last Saturday in Cockeysville, Md., after 12 days of trying to mediate a settlement in the dispute, announced in San Francisco that the talks would resume. He made no other comment.

Kagel's anouncement followed telephone conversations with Ed Garvey, executive director of the NFLPA, and Jack Donlan, executive director of the NFL Management Council, the league's labor negotiating arm.

In other developments in the players strike, which enters its 38th day today:

* A complaint was made on behalf of the general counsel of the National Labor Relations Board charging the NFL with failing to bargain in good faith and with causing and prolonging the strike.

* In response to a question, the NFLPA said that Washington Redskins season ticket holders have, in effect, given the club an interest-free $6.9 million loan from tickets that have gone unused because of the strike. In today's investment circles, such a sum would earn $690,000 a year if invested. Gerard T. Gabrys, Redskins' senior vice president, said all season ticket holders would get their money back for any games not played, but declined further comment.

* The NFL confirmed that it will not receive a television advance from the networks Nov. 1, the first month it has not received a television advance despite the Sept. 20 commencement of the strike. The league received a $20 million television advance last spring, $75 million in September and $37.5 million in October, although only two weekends of regular-season games were played. The networks must receive a refund or an equivalent form of compensation.

There was no immediate indication why Kagel had called for a resumption of the talks.

Art Modell, owner of the Cleveland Browns and a member of the NFL's television committee, said the fact that Kagel is resuming the talks "holds some promise."

But he added, "I'm not very sanguine about it. We're racing against the clock and racing against the elements."

Modell, in New York yesterday to discuss television arrangements and poststrike schedules with Tex Schramm of the Dallas Cowboys and NFL Commissioner Pete Rozelle, repeated that a "12-game schedule is the minimum number necessary to preserve a totally credible season."

But he added that since only two games of the regular-season 16-game schedule can be made up, there would have to be a settlement and players "in the camps by Monday morning for six solid days of reconditioning" before the Nov. 7 games. This weekend's games have already been called off.

Modell also said "it is not our intention to call off the season at all as long as there is a chance of playing games," but he warned that "the season could evaporate all by itself."

There was no indication from either side of a basic change in position: the union's demand for a seniority-based wage scale with performance incentive bonuses tied to a central fund and the NFL's opposition to that concept.

But Modell said NFL negotiators were studying the players' five main points of concern that they want in a settlement. These include an immediate and substantial wage increase, protection for older players from being cut for economic reasons, performance incentive bonuses, elimination of wage inequities, and a guaranteed share of any future television revenues.

The NLRB complaint, filed as announced last Friday by its New York regional director on behalf of general counsel William A. Lubbers, charged that since Feb. 16, the NFL has failed to bargain in good faith by "insisting that the players association waive its right to bargain collectively as to compensation to be paid to the employes . . . " The complaint also said the "concerted work stoppage and strike was caused and prolonged" by the NFL.

A hearing on the complaint was set for Nov. 15 before an administrative law judge in New York. A spokesman for the management council said the league was guilty of no wrongdoing and repeated its contention that issuance of the complaint was no more than the legal equivalent of the filing of a lawsuit.

Concerning the advance season ticket sales, the management council said all clubs have been instructed to refund ticket holders their money for any games not played because of the strike but the method for doing this has been left to the individual clubs, which are each losing an estimated $1.23 million a week, according to the NFL.

Some teams have already begun giving season ticket holders their money back, but most, like the Redskins, are awaiting conclusion of the strike. No teams could be found that were paying fans interest on their season tickets, which, in the case of the Redskins, had to be paid for in full in the spring.

"The public and the networks are funding the strike," contended NFLPA economist Michael Duberstein. He said most clubs, in addition to their share of the $132.5 million the NFL has received in television advances, have advance ticket sales of between $5 million and $6 million, which generally is invested in interest-bearing accounts during the offseason when expenses are at a minimum.

But Jim Miller, a spokesman for the management council, said audits show that overall the clubs borrow more during the offseason to meet expenses than they receive in advance season ticket sales. He said the average NFL club pays out $121,000 more a year in interest than it takes in.

Duberstein disputed the audit, however.

"If they make so much money, why do they have to borrow?" he said.