SAN DIEGO -- Houston Astros left-hander Dallas Keuchel outpitched San Diego Padres right-hander Andrew Cashner and left fielder Colby Rasmus broke a 1-1 tie with a two-run homer in the fourth inning as Houston defeated the Padres 7-2 on Wednesday to complete a three-game sweep at Petco Park.

The win was the sixth straight for the Astros (14-7), who are 10-2 on the road this season -- a franchise record for the first 12 games. The American League West leaders have won 10 of their last 11 games.

Meanwhile, the Padres (11-12) fell to 1-5 on their homestand. They have lost seven of their last eight games since a 10-5 start, resulting in their fifth straight losing record in April.

Cashner opened the game by striking out the first six Astros he faced -- breaking the old Padres record by two and coming within two strikeouts of the major league record. But the next hitter he faced, center fielder Jake Marisnick, doubled to lead off the third and scored the Astros' first run.

Keuchel improved to 3-0 with a 0.73 ERA five starts. He allowed one run on three hits and no walks over eight innings. He struck out four while facing three hitters over the minimum. Keuchel retired 22 of the last 23 hitters he faced, including 14 in a row after left fielder Matt Kemp's first-inning, run-scoring double.

The Padres entered the game hitting a major-league-best .345 against left-handed pitchers and struck quickly against Keuchel.

Center fielder Wil Myers singled to lead off the Padres' first and scored on Kemp's one-out double to right-center.

But Keuchel got Padres left fielder Justin Upton to pop out to second with Kemp at third and one out -- starting a run of 14 Padres retired before Cashner led off the bottom of the sixth with a single to center.

Meanwhile, the Astros tied the game in the top of the third and took the lead on Rasmus' two-run homer in the fourth.

After Cashner had struck out the first six hitters he faced -- setting the Padres' record for consecutive strikeouts to open a game -- Marisnick opened the third with a double to left. Catcher Hank Conger walked.

With runners on first and second, Keuchel was trying to bunt when the ball got away from reserve catcher Wil Nieves, allowing Marisnick to reach third. Marisnick scored on second baseman Jose Altuve's sacrifice fly to left.

With one out in the fourth, Astros right fielder George Springer doubled and Rasmus immediately followed with a 425-foot drive into the right-field seats. It was Rasmus' fourth homer of the season and the fifth allowed by Cashner.

Cashner worked seven innings, giving up three runs (two earned) on six hits and a walk, with a season-high 10 strikeouts.

The Astros scored four more runs in the top of the ninth.

NOTES: Padres RHP Andrew Cashner started the game by striking out six straight Astros, two shy of the major-league record. The Astros have yet to name a starter for Friday's game against Seattle in Houston, although right-handed reliever Samuel Deduno (0-0, 2.89 ERA) was expected to get the call if he didn't pitch in relief Wednesday in San Diego.