The Nationals were unable to complete a sweep of the Mariners Sunday night as the team lost to Seattle, 5-2, in the final game of the three-game series at Safeco Field. Things got off to a good start for Washington after a monster solo home run off the bat of Bryce Harper in the top of the second gave the Nationals an early lead against Mariners starter Hisashi Iwakuma. Washington made it a 2-0 game an inning later on a home run by Nate Schierholtz.But with the Nationals staked to a two-run lead heading into the bottom of the third, the Mariners began to battle back against Roark. Seattle made it a 2-1 game in the third on an RBI single by Dustin Ackley. Usually, when Roark is on his game, leading by only one run in the fifth inning is not a huge concern for Washington. Unfortunately for Roark and the Nationals, Ackley was only getting started. After another homer by Harper gave the Nationals a temporary 4-2 lead in the fifth, the Mariners mounted another rally in the bottom of the frame. With one out and runners on first and second, Ackley crushed a 2-0 fastball from Roark into the seats in right field, giving Seattle a 4-2 lead. The Mariners added another run in the bottom of the eighth on an RBI double by Endy Chavez. With the loss and Atlanta’s win over the Marlins, the Nationals are 77-58 on the season and lead the Braves by six games in the NL East. Next game: Gio Gonzalez (6-9, 3.86 ERA) and the Nationals take on Roberto Hernandez (2-1, 3.52 ERA) and the Dodgers Monday night in a battle of two first place teams. First pitch is scheduled for 8:10 p.m. ET.