The loss reduces the Nats’ lead over the Chicago Cubs for the top spot in the NL wild-card race to a half-game, and the streaking Milwaukee Brewers, winners of 10 of their last 11, are a game and a half back of Washington for the second spot.
The Nationals have lost eight of their last 12 games.
Stephen Strasburg struggled with pitch counts all night, needing 99 pitches to get through five innings, allowing two runs on three hits, striking out six and walking four.
Sean Doolittle (6-5, 4.11 ERA) was saddled with the loss in the scorebook, but all he did was surrender a walk while recording two outs in the seventh.
Hunter Strickland relieved Doolittle, and walked a batter and threw a wild pitch to advance both runners into scoring position, ahead of a two-run double by Ozuna.
The Nats (82-67) send Patrick Corbin (12-7, 3.20 ERA) to the mound to face Cardinals starter Miles Mikolas (9-13, 4.28 ERA) Tuesday night in Game 2 of the teams’ three-game series.
Story by Chris Graham