Washington Nationals closer Jonathan Papelbon filed a grievance against the club for failing to pay him during a four-game suspension that he served during the 2015 season, per Rob Bradford of WEEI in Boston.
The issue at hand is whether the Nationals owe him the salary they did not pay during his suspension. According to Bradford, Papelbon claims "there is no precedent of a player having his salary withdrawn after such a team-issued suspension."
Here is video footage of the incident that resulted in Papelbon's suspension, per MLB.