Bryce Harper (34) and Jonathan Papelbon (58) fight in the dugout in the eighth inning. (Jonathan Newton / The Washington Post)

Somehow — and frankly, it seemed impossible — the disappointing chaos of this 2015 Nationals season escalated further Sunday afternoon after Jonathan Papelbon and Bryce Harper had to be separated in the Nationals dugout in the eighth inning of the Nationals 12-5 loss.

Harper popped out to short left field, put his head down, and jogged slowly to first. He did not run the ball out at full speed, and Papelbon appeared to take issue with it. As Harper walked back to the dugout, taking off his batting gloves, Papelbon appeared to mouth “run that out” at the 22-year-old MVP candidate. Harper fired back, and the two exchanged words until Harper got back into the dugout, a step below Papelbon. From what was visible on television replays, Harper appeared to tell Papelbon something along the lines of “bring it on” (in less polite terms). Then Papelbon reached for Harper’s throat, and the right fielder did the same. Ian Desmond — who would get a curtain call for his years of Nationals service a few minutes later — pulled Harper away as other teammates held Papelbon back.

Papelbon had come in to get one out in the eighth inning. He stayed in for the ninth. Harper did not go back to right field for the ninth, replaced in the lineup by Tyler Moore, who came in to left field and pushed Matt den Dekker to Harper’s spot in left. Papelbon continued to pitch, then allowed a go-ahead home run to Andres Blanco. He could not escape the ninth, and walked back to the dugout with his head down, cap pushed up his forehead, greeted by few of his teammates.

We will update with more reaction after the game.