The NFL Players Association is on the brink of filing a collusion grievance against NFL owners based on a case it has been building since only one of 216 restricted free agents was signed to an offer sheet during the offseason, according to union sources.

NFLPA executive director DeMaurice Smith is reviewing the case that has been collected by his legal team and is expected to approve a collusion filing with the Special Master by Wednesday's deadline, as dictated by the current CBA. The Dec. 8 deadline is established as within 90 days of the regular-season opener, which was Sept. 8.

While many details have not been revealed, union sources concede that previous reports of a collusion case center on the lack of activity with the 216 restricted free agents, whose number quadrupled in size because of the uncapped-year rules in 2010. The union has gathered what it believes is similar dialogue that a variety of teams expressed when communicating with agents who represented the players, a source said.

Saints running back Mike Bell was the only restricted free agent to sign an offer sheet. The Philadelphia Eagles acquired his services when New Orleans declined to match the offer.

While Bell's signing represented less than 1 percent of the restricted free agent class in 2010, the comparison to 2009 is debatable, inasmuch as only four of 55 RFAs, or 7 percent, were signed to offer sheets with none changing teams.

Jeff Pash, the NFL's vice president of legal counsel/labor and point man, has previously stated that the uncertain labor future in 2011 accounted for the lack of restricted free agent activity.

The union's collusion charges, if filed, include other elements of what it considers illicit activity, a source said.

However, even while union and management are making plans in the event of a work stoppage on March 4 when the CBA expires, sources on both sides concede that negotiations will continue and could produce a new agreement before that deadline. Compromise on many issues, including the salary-cap formula, is still very possible, sources said. Pash told the SportsBusiness Journal in an interview last week that he expects a deal to be completed by March 3.

Until then, the rhetoric and activity have been cast as gloomy as the league and union negotiate over financial matters and an 18-game regular season.

If the union actually files collusion charges this week and Special Master Stephen Burbank allows the case to proceed, it could benefit the union's mission to gather discovery on management documents.

NFL owners and team executives will convene Dec. 15 in Fort Worth, Texas, next week to discuss labor matters.

Chris Mortensen is ESPN's Senior NFL Analyst.