NFL Commissioner Roger Goodell, left, and National Football League Players Association executive director DeMaurice Smith speak to the media outside of the Ritz-Carlton hotel after addressing players during the NFLPA rookie symposium last month in Sarasota, Fla. (BRIAN BLANCO/ASSOCIATED PRESS)

Working out the details of a rookie pay system is among the final remaining negotiating obstacles for the NFL and locked-out players as they attempt to complete a deal to end the sport’s nearly four-month shutdown in time to preserve a full preseason, according to people not involved in the talks but familiar with them.

Differences between the two sides on how a rookie compensation system would work contributed heavily to the talks slowing Friday during a negotiating session in New York, said those people, who spoke on the condition of anonymity because of the sensitivity of the deliberations.

The league wants to significantly curb the amount of guaranteed money in the contracts of players selected early in the NFL draft. People familiar with the talks said the players’ side is willing to agree to a system that diverts money from rookies to veterans. But the players are resisting a system as restrictive as what the league is seeking, those people said.

The two sides apparently are at odds mostly over how such a system would work for the players drafted in the upper portion of the first round, perhaps the first eight or so players selected. The length of the contracts to which those players could be signed could be an issue, along with the amount of guaranteed money in their contracts.

There has been speculation within the sport that other issues, potentially including court oversight and rules for free agency, could be problematic as well.

The league does not want the sport’s labor situation to be subject to ongoing oversight by a federal court. That potentially could be avoided if the two sides agree to a labor deal and the players separately withdraw their antitrust lawsuit against the owners in a federal court in St. Paul, Minn. The court would have to approve a prospective deal between the league and players if it is done as a settlement of the players’ lawsuit. But even under those circumstances, the deal potentially could contain provisions to limit future court oversight. It appears the two sides are likely to find a compromise on that issue.

Free agency considerations are not regarded as likely deal-breakers, either. The league reportedly wants teams to be given the right of first refusal for an additional few unrestricted free agents this offseason — allowing the teams to retain those players by matching any contract offers by other clubs — and the players’ side is said to be resisting.

The league and players appear close to an accord on the central economic issue of the dispute: how to divide the sport’s burgeoning revenues. Face-to-face talks are to resume Monday in New York between attorneys and staff members for the two sides, and owners and players are to rejoin the negotiations later in the week. People familiar with the talks said a deal by the end of the week remains possible, and time is running short for the two sides to salvage the Aug. 7 preseason opener.

The league and players are scheduled to meet July 19 with their court-appointed mediator, Chief Magistrate Judge Arthur J. Boylan. In the meantime, negotiations are to continue without Boylan’s supervision.