The NFL Players Association is preparing a possible collusion case accusing teams of improperly conspiring to restrict players' salaries last offseason, people familiar with the preparation of the case said Friday. The case potentially will be filed within the next month, said one individual, who like the others spoke on the condition of anonymity because the union has made no announcement about its intentions. The collective bargaining agreement between the league and the players' union prohibits a team from entering "into any agreement, express or implied" with another team "to restrict or limit" contract negotiations with players or players' salaries. George Atallah, the union's assistant executive director of external affairs, said a possible collusion case is being researched but declined to comment on the details. "The players continue to gather evidence on possible collusion," Atallah said Friday. An NFL spokesman declined to comment. Source: The Washington Post