WASHINGTON -AP- Wilmer Difo hit his first major league homer, andPedro Severino his second, helping the injury-depleted NL East championWashington Nationals move closer to clinching home-field advantage in the Division Series by beating the Arizona Diamondbacks 5-3 at a near-empty stadium on a dreary Thursday. Second baseman Difo and catcher Severino, both rookies, were in the lineup instead of Daniel Murphy (last started 12 days ago) and Wilson Ramos (out for the season), respectively.Last in the NL West, Arizona has nothing at stake the rest of the way. The Nationals, while already assured of winning their division and of facing the Los Angeles Dodgers to open their postseason, still are trying to lock up a higher seeding for that series.Washington began Thursday with a two-game lead over NL West champion LA for the right to host more games in the best-of-five NLDS. The Dodgers, though, hold the tiebreaker because of a 5-1 advantage in the teams' season series.Nationals starter Joe Ross, working his way back from a stay on the disabled list with right shoulder inflammation, allowed one run in four innings, throwing 90 pitches. Washington wants to stretch him out to be able to start at some point in the playoffs.Reliever Reynaldo Lopez (5-3) was credited with the win. He pitched 3 2/3 innings, letting up Socrates Brito's two-run homer in the ninth before being lifted.Mark Melancon got the last two outs for his 45th save.Robbie Ray (8-15) allowed five runs in 4 2/3 innings, including solo shots by Severino in the third and Difo in the fifth, along with Michael A. Taylor's two-run single in the fourth.