Kazuo Matsui sparked Houston's seven-run rally with a two-run single, and the Astros coasted to their fourth straight victory Wednesday night, 9-3 over the unsettled Cincinnati Reds.

Houston has won four in a row for the first time since last May, getting 36 runs out of a lineup producing top-to-bottom.

Ken Griffey Jr. hit his 597th career homer off Chris Sampson (1-2), the only bright moment for the struggling Reds, who changed general managers before the game. Walt Jocketty took over for Wayne Krivsky, a show of impatience by team owner Bob Castellini.

Jocketty watched from an upstairs booth as the Reds lost for the ninth time in 12 games. At 9-13, they're off to their worst start in five years.

If right-hander Bronson Arroyo (0-3) doesn't get turned around, the outlook is dreary.

The Astros knocked Arroyo out of the game by sending 11 batters to the plate in the fourth inning for seven runs. Matsui, who has delivered three pivotal hits since he returned from the disabled list, had the first of six straight off Arroyo and reliever Mike Lincoln.

Arroyo gave up 10 hits, a walk and eight runs in 3 2-3 innings, raising his earned run average to 7.56.

A day after the Astros set a season high for runs in an 11-7 win over the Padres, their lineup continued to string hits together. Every starter except Sampson had at least one.

Darin Erstad and Hunter Pence led the way with three hits apiece.

It was another impressive showing by the Astros in a ballpark where they have dominated lately. They're 9-1 at Great American Ball Park over the last two years, and 25-15 since it opened in 2003.

The big, early lead helped Sampson rebound from the worst start of his career. The right-hander retired only two batters last Friday in Colorado, giving up six runs and six hits in an 11-5 defeat.

Ahead 9-1 in the fourth, Sampson could challenge a lineup that has struggled all month, a big factor in Krivsky's firing. Sampson allowed eight hits and two runs in seven innings.

Griffey's solo homer in the first inning was his first in a span of 22 at-bats and left him three shy of joining Barry Bonds, Hank Aaron, Babe Ruth, Willie Mays and Sammy Sosa with 600 homers.

It was Griffey's first homer on a seven-game homestand that concludes Thursday. The Reds will play nine games in San Francisco, St. Louis and Atlanta. Griffey hit his 200th, 300th, 400th and 500th homers in road games.

Notes:@ The seven-run inning was Houston's biggest since it scored seven in the fourth inning last July 29 against San Diego. ... Pence extended his hitting streak to six games. ... Griffey's 199th homer with the Reds moved him ahead of Barry Larkin for eighth place on the franchise list. Griffey came to his hometown team in a trade with Seattle before the 2000 season. ... 3B Edwin Encarnacion extended his hitting streak to a career-high 13 games with a solo homer in the ninth. ... The Reds are 0-8 in series openers.

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