Adam Dunn hit a two-run homer off Edinson Volquez, who had a rough time in his second start since elbow surgery, and the Washington Nationals beat the Cincinnati Reds 7-1 on Thursday for a split of their four-game series.

Volquez (1-1) dominated Colorado last Saturday in his return from reconstructive elbow surgery. He had control problems the second time out, walking four and giving up six runs in only 2 1-3 innings.

Dunn’s only hit in the series was his two-run shot in the third inning, his 23rd homer of the season. Leadoff hitter Nyjer Morgan reached base four times and had a career-high three steals.

Livan Hernandez (7-6) allowed seven hits during his second complete game, getting his first victory since June 21. He also singled home a run off Volquez.

Hernandez threw 102 pitches, didn’t walk a batter and struck out five during his third career win against Cincinnati, his fewest against an NL team. He’s 3-7 in 15 career starts against the Reds.

The Nationals won back-to-back road games for the first time since May 12-13. They’ve gone 8-26 on the road since then.

Washington arrived in town with a slumping offense, but scored 22 runs in the last three games against a pitching staff that has been the best in the NL since June 17.

The Reds are hoping that Volquez’s return from surgery last August helps them stay in contention with St. Louis in the NL Central. They were greatly encouraged when he allowed only three hits and one run in six innings of an 8-1 win over the Rockies on Saturday, striking out nine with a fastball that regularly clocked 95 mph.

Against the Nationals, his pitches were out of control. He walked three consecutive batters in the second, then gave up a single by Hernandez. Dunn homered in the third, his first hit in an otherwise drab series against the team that traded him away in 2008 — 1 for 15 with six strikeouts. It was his 126th homer at Great American Ball Park, the most by any player.

Cristian Guzman followed with a triple off the yellow padding atop the wall in right — the umpires reviewed to make sure it wasn’t a homer and upheld the call. When Willie Harris followed with a single, manager Dusty Baker decided it was enough for Volquez, who threw 75 pitches but only 38 strikes.

NOTES: Hernandez has both of the Nationals’ complete games. ... Dunn is batting .182 career against the Reds with two homers. ... Nationals manager Jim Riggleman said RHP Luis Atilano will probably go on the 15-day DL. Atilano complained of a sore arm after his 8-7 loss to the Reds on Tuesday. ... The Reds activated C Ramon Hernandez and sent C Corky Miller to the minors. Hernandez, who had been out with a sore knee, played 1B, giving Joey Votto a day of rest.