NASHVILLE -- Nationals closer Jonathan Papelbon has filed a grievance against the organization because he wasn't paid for the final four games of the 2015 season, a baseball source told to MLB.com. The Nationals did not confirm the report.

Papelbon's season came to an end on Sept. 28 when the Nationals announced that he had been suspended for the final four games of the season without pay for his confrontation with outfielder Bryce Harper in a 12-5 loss to the Phillies on Sept. 27.

With the score tied at 4 and the Nationals batting in the eighth inning, Papelbon and Harper got into an argument in the dugout before engaging in a physical altercation, during which Papelbon grabbed Harper's neck. Coaches and teammates had to break up the altercation.

Papelbon said Saturday he and Harper had settled their differences. Harper accepted Papelbon's apology.

"My mistake was doing that in the dugout in front of a camera," Papelbon said. "I've got two young kids. They know that's not right, but it happens. I fully apologize for doing that but most of it's handled in the tunnel. [Harper is] a competitor, too."

Another baseball source said the Nationals are trying to trade Papelbon. They are trying to acquire Reds closer Aroldis Chapman, but the price might be prohibitive.