The MLB Player’s Association has filed a grievance action against the Astros relating to the team’s recent failure to sign top overall draft choice Brady Aiken, reports Murray Chass. Ken Rosenthal of FOX Sports also reports the filing, via Twitter.

Though details remain vague, it appears that the union’s action alleges that Houston inappropriately manipulated the signing situations of Aiken and fifth-rounder Jacob Nix after a dispute arose over Aiken’s medicals. Ultimately, the Astros reportedly offered Aiken only $5MM after having reportedly agreed to a $6.5MM bonus. The club also did not go forward with signing Nix after having reportedly agreed to sign him for $1.5MM.

Having failed to sign Aiken, inking Nix to that reported over-slot bonus would have put the Astros well above their pool allocation for signed players and subjected them to the penalty of forfeiting each of their next two first-round choices. As MLB.com’s Jim Callis has explained, some have charged that Houston sought to sign Aiken at the lower price tag in order to make a run at 21st-round choice Mac Marshall, who had previously announced that he would go to college. Of course, it remains to be seen what precise allegations have been made by the union.

While the result sought in the grievance proceeding remains unknown, presumably the MLBPA could seek some relief for Aiken and/or Nix if not also some action against the club. As things stand, the pair of hurlers face the decision whether to matriculate at a university (both were UCLA commits) or play junior college ball and re-enter the draft next year.