Edinson Volquez pitched 7 1-3 strong innings and the Cincinnati Reds scored a pair of unearned runs to beat Houston 2-1 and push the Astros to the brink of elimination Tuesday night.

With the Mets' win over Chicago, Houston fell 4 1/2 games behind New York with five games to go. A loss and a Mets win Wednesday could eliminate the Astros from the playoffs.

Volquez (17-6) won in his fifth attempt to get his 17th victory. He had three no-decisions and a loss since winning Aug. 29 against San Francisco. He allowed one run, struck out nine and scattered six hits in the longest outing of his career. He walked one.

Francisco Cordero pitched the ninth for his 34th save in 40 tries. He got Ty Wiggington to hit into a line drive double play with the tying run on second.

Wandy Rodriguez (8-7) gave up two unearned runs in five inning and six hits. He struck out seven and walked two.

The Reds scored in the first when Joey Votto's looping fly to left was misplayed by Ty Wigginton for a three-base error. That drove in Jeff Keppinger, who had singled.

Jolbert Cabrera then drove in Votto with a single to make it 2-0.

Kazuo Matsui led off the first with a home run to left. It was his sixth of the season.

In the seventh inning, umpires used the instant replay to verify a hit by Votto was not a home run.

Replays appeared to show the ball hit the top of the right-field fence, bounced into an empty seat and rebounded back on the field. But officials ruled it stayed in play for a single.

Notes:@ It was the ninth time in his career Matsui has led off the game with a home run. It was the third time this season, the last coming Aug. 8 at Cincinnati. ... Volquez recorded his 200th strikeout of the season in the second inning. He now has 206. Volquez had pitched seven innings 10 times this season. The win marked the first time a Reds starter has reached 17 victories since Pete Schourek went 18-7 in 1995. ... Reliever Chris Sampson left the game in the seventh inning with right lateral epicondylitis, or tennis elbow. He is day-to-day. The replay timeout was the second instant replay call at Minute Maid Park. The first was when Hunter Pence's double was confirmed against Pittsburgh Sept. 9.