The Nationals had a 6-4 lead going into the bottom of the ninth, but Papelbon was able to get just two outs. The inning started with Alex Gordon, who led off with a check-swing single. Salvador Perez followed with a single to left, putting runners on first and second.
After Omar Infante struck out, Mike Moustakas came in as a pinch-hitter. Moustakas was a strike away from being the second out of the inning, but he singled to center field, scoring Gordon and pinch-runner Terrance Gore to tie the game at 6.
After Jarrod Dyson flied out to left fielder Chris Heisey for the second out of the inning, Alcides Escobar singled to put runners on first and third. Lorenzo Cain followed and was a strike away from making this game an extra-inning affair. But he singled past center fielder Michael Taylor to score Moustakas and end the game.
"With Papelbon, it was just location," catcher Wilson Ramos said. "He just didn't locate. He left the ball in the zone. [The Royals] have bats. Obviously, they know how to use them. They put the ball in play and were able to get hits.
Papelbon's ERA climbed to 4.50, but manager Dusty Baker is going to stick with him as the closer.
"Pap has been good. He has been very good. But there is nothing to say. The Royals took that game from us," Baker said.
Bill Ladson has covered the Nationals/Expos for MLB.com since 2002 and writes an MLBlog, All Nats All the Time. He also can be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.