Mediator Sam Kagel was reported tonight to be prepared to recess negotiations between the National Football League and the striking NFL Players Association and return to his home in San Francisco.

Kagel, who since Oct. 12 has been attempting to negotiate a settlement in the strike, reportedly told both sides that negotiators are "spinning . . . wheels" and that he plans to fly home Saturday.

It was learned that NFLPA leaders feared that Kagel might recommend that the players return to work while the dispute was referred to a form of arbitration. The union has adamantly opposed returning to work without a ratified contract.

The sides are scheduled to meet Saturday morning, but indications were that the meeting would be short. Kagel, 73, reportedly is tired, unhappy with the lack of progress and eager to return to business interests in San Francisco.

Earlier, Ed Garvey, executive director of the NFLPA, said the union is willing to reconsider its demand for a wage scale tied to a fund if that becomes the only obstacle to settlement.

He said the union is flexible on the trust fund if management will negotiate on wages. "We're certainly willing to take a hard look at it if that's the only thing that's holding things up," he said.

But later he said his remarks were "not a significant development; it's not a development at all."

He said the position on the central fund is one that the union has had since before the strike began. Management wants to retain the system of players negotiating their contracts individually.

Union sources said the NFLPA is willing to move away from its demand for a trust fund if it can protect older players from being cut.

"Our real concern is protecting the older players; if there is another way to do it, that's all right with us," said one union official. Since the strike began, the union's key demand has been that the NFL contribute to a trust fund that would pay player salaries on a seniority-based scale with performance-incentive bonuses.

The theory behind this concept is that a trust fund would eliminate any economic motivation for clubs to cut older players because of their higher salaries. With all salaries coming from a trust fund, an NFL club's costs wouldn't be affected by a salary paid to a particular player.

Today, for the first time, negotiators concentrated on the basic issue of the wage scale. But Kagel was pessimistic at his afternoon media briefing. Stressing that his report was authorized by both sides, he said, "We are continuing to meet on basic money issues, and I cannot report any substantial progress on this subject."

Negotiations were recessed this afternoon as the sides caucused. Talks resumed this evening, then ended before 9.

Kagel was asked what was holding up a settlement. "M-o-n-e-y," he said.

In another development, management sources confirmed the details of an agreement worked out last week concerning the controversial issue of requiring players to undergo mandatory urinalysis.

That agreement permits club physicians to run tests on players as part of preseason physical examinations and during the year if the physician thinks there is cause for urinalysis. But the clubs will not be permitted to test players randomly.

Since publication last June in Sports Illustrated magazine of a first-person account of his involvement with cocaine by former NFL player Don Reese, the issue of drug usage in the league has been highly controversial.

The union has scheduled a meeting of player representatives from all 28 teams in Washington Sunday afternoon. Garvey said he hopes to attend the session, but would be at the bargaining table if Kagel prefers. The agenda for that session will be a briefing of the player representatives on the status of negotiations here and discussion of the prospect of forming an NFL players league if the NFL cancels the season.

Under that concept, the players would form teams of their own in NFL franchise cities and play an approximation of the regular NFL schedule. The Atlanta-based Turner Broadcasting System has expressed an interest in televising such games.