John Lannan pitched 7 2/3 strong innings and drove in a pair of runs as the Washington Nationals cruised to a 4-2 victory over the struggling St. Louis Cardinals.

Michael Morse belted a two-run homer while Adam Dunn went 2-for-3 and scored twice for the Nationals, who won three of the four games against the Cardinals.

Lannan (6-6) improved to 1-2 in five career meetings with St. Louis, allowing one run and eight hits. The left-hander struck out four without a walk in winning for the fourth time in five starts.

After escaping a jam in the first inning, Lannan helped his own cause in the second. Dunn and Morse opened the frame with singles and three batters later, Lannan doubled to left field, giving Washington a 2-0 lead.

The Nationals doubled the advantage in the next inning. Dunn drew a two-out walk before Morse, who collected a career-high four hits on Saturday, hit his 10th home run of the season.

Washington did all its damage against Adam Wainwright (17-9), who surrendered four runs and six hits over five innings en route to his third straight loss. The right-hander walked three and struck out seven to drop to 6-8 on the road and fail to join CC Sabathia of the New York Yankees as the only 18-game winners in the major leagues.

Drew Storen served up a solo homer to Pedro Feliz in the ninth before notching his third save in four chances.

Jon Jay also had an RBI groundout for the Cardinals, who have lost 10 of 14 and dropped to 2-5 on their season-high 10-game road trip.