The owners have agreed to sweeteners, including expanded rosters, more players on practice squads, higher minimum salaries and reductions in the number of full-contact practices and preseason games. The players would also receive 48.5 percent of shared revenue (compared with 47 percent now), enhanced medical and pension benefits, and more lenient testing for marijuana.

Many of these elements may mean little to players with eight- and nine-figure contracts. But they are likely to appeal to younger players on the fringes of the game, who make up the bulk of union membership.

“The deal is better from the perspective of an incoming player or someone who is one to three years in the league,” said Jodi Balsam, who worked as a lawyer at the N.F.L. and now teaches at Brooklyn Law School. “The league is trying to sweeten the pot by cutting back on training camp and getting rid of a preseason game, but when it comes down to the dollars, it probably doesn’t make sense for a veteran player to vote yes."

The players are discovering other potential trap doors, including an item listed at the end of a fact sheet the union distributed to players last week that claimed that under the proposal, filing workers’ compensation claims would be made easier. Brad Sohn, a lawyer who has represented players in cases against the N.F.L., said that he believed the change would force players to file disputes with an arbitrator, not the courts, which would eliminate potential damages a player could receive and close off a remedy if players believe a team has been negligent in handling their injury.

“There would be an arbitration mechanism, but the courtroom doors would be locked,” Sohn said. “You are removing the ability to hold anyone accountable.”