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Ramon Hernandez and Jay Bruce hit back-to-back homers in the fourth inning to break a scoreless tie and the Cincinnati Reds beat the Arizona Diamondbacks 9-5 on Thursday night.

The victory gave the Reds a three-game sweep over the NL West cellar dwellers, and was Cincinnati’s sixth straight win overall, the team’s longest streak of the season.

The Reds took a season-high 3½-game lead over the St. Louis Cardinals for first place in the NL Central.

Hernandez, on a .360 tear with two home runs since coming off the disabled list on July 22, blasted a three-run shot to left field on the first pitch he saw from Joe Saunders (7-13). Bruce followed with his second homer in as many nights. It was the seventh time the Reds hit back-to-back homers this season.

Travis Wood, called up from Triple-A Louisville on Thursday to join the starting rotation for the time being, lasted 6 1-3 innings and allowed one run and four hits with six strikeouts. Wood (4-1) lowered his ERA to 2.51.

Hernandez’s homer drove in Scott Rolen, who had walked, and Jonny Gomes, whose single put runners at first and third with one out.

The Diamondbacks made it 4-1 on Mark Reynolds’ 27th home run in the bottom of the fifth.

Saunders gave up four runs and eight hits over six innings and lost his third straight game in his fifth start with Arizona.

The Reds added the rest of their runs in the eighth after a two-out fielding error by Diamondbacks’ left fielder Rusty Ryal, who dropped what should have been the third out after making a catch. A walk and pinch-single by Laynce Nix followed, then another walk and Drew Stubbs’ two-run single.

The Reds (70-51) put five runs on the board in the eighth, capped off with Joey Votto’s two-run double. Votto was back in the lineup after missing Wednesday’s game with a sore back.

The Diamondbacks had a four-run eighth that included a three-run home run by Chris Young.

Notes: To make room for Wood, the Reds optioned RHP Carlos Fisher to Triple-A Louisville. Fisher’s designation meant that rookie Mike Leake, who has started 22 games but struggled in his past two, was moved to the bullpen. Manager Dusty Baker said Fisher will get a September call-up. The official scorer changed what was ruled a sacrifice fly and RBI for Nix on Wednesday in the eighth inning to a fly out with no RBI and an error on Arizona RF Justin Upton for an overthrow of home plate. Hernandez scored on the play.