Nationals 9, Orioles 3: Adam LaRoche hit two home runs and Tyler Moore and Roger Bernadina delivered back-to-back shots in a four-run fourth inning as host Washington routed Baltimore.

Moore delivered a two-run blast into the Orioles bullpen with one out to make it 5-3, Bernardina's home run came four pitches later and Denard Span capped the uprising with a two-out RBI double. Zach Duke (1-1) earned the victory by recording five outs on eight pitches.

Chris Davis hit his major league-leading 17th home run and J.J. Hardy followed two batters later with his 10th to tie the game 3-3 in the fourth inning for the Orioles. Hardy finished with three hits as Baltimore had its team-record streak of scoring five or more runs in a road game end at 10.

Washington's Nathan Karns made his major-league debut and allowed three runs, five hits, walked two and struck out three in 4 1/3 innings. Baltimore's Kevin Gausman (0-2) was roughed up for seven runs and eight hits in four innings in his second major-league start and saw his ERA rise to 11.00.

After Span was retired in the first inning, Steve Lombardozzi and Ryan Zimmerman singled to center before LaRoche drove Gausman's fastball over the right-center field wall. LaRoche's second homer - into the Nationals bullpen in right - was a solo shot in the eighth for his third multi-homer game of the season.

GAME NOTEBOOK: Washington RF Bryce Harper (bursitis in left knee) missed his second straight game and is unlikely to play Wednesday at Camden Yards in Baltimore. ... Orioles RF Nick Markakis went 0-for-4 to end his hitting streak at 12 games. ... The game was delayed at the start for 1 hour, 30 minutes because of rain.