HOUSTON -- Having witnessed the power display of Diamondbacks sluggers Paul Goldschmidt and J.D. Martinez a half-inning earlier, Astros right fielder Josh Reddick tapped into his own power reserve to help Houston thwart Arizona's comeback attempt.

Reddick capped a four-run eighth inning with a line-drive, two-run homer, and the Astros claimed a 9-5 win over the Diamondbacks on Wednesday night at Minute Maid Park.

Reddick homered against Arizona left-hander Andrew Chafin to right field, his first homer against a southpaw this season, to plate George Springer.

The Astros (74-46) scored earlier in the inning via a wild pitch and a Jose Altuve sacrifice fly that brought home Derek Fisher.

"It was good to see everybody come together that one inning and give us the insurance that we needed," said Reddick, who finished 2-for-5 with three RBIs.

"(The home run) was huge for me. I've taken a lot of pride in doing better against lefties this year, not trying to hit homers off of them. Just trying to get good pitches."

Arizona (66-54) shaved a 5-1 deficit to one run with back-to-back homers in the eighth.

Goldschmidt, a native of Houston suburb The Woodlands, socked a two-run blast to left field, his 29th homer of the season, off Astros right-hander Luke Gregerson before Martinez, a former Astro, followed with his 24th home run of the season. It was Martinez's eighth long ball since joining the Diamondbacks last month.

"We showed a lot of battle," Arizona manager Torey Lovullo said. "I know things didn't get off the right way for us, but I think something clicked offensively for us, and Goldy's home run set a really good tone for what we were ready to do.

"Unfortunately, we didn't have a shutdown inning. Those things are things that you kind of expect, and then go back out and potentially tie the game up, and we didn't."

Five different Astros had RBIs against Diamondbacks starter Taijuan Walker (6-7).

Designated hitter Carlos Beltran opened the scoring with his 14th home run, a solo shot with two outs in the second inning. Beltran added a sacrifice fly an inning later, upping the Houston lead to 3-1 after Marwin Gonzalez worked a bases-loaded walk to break a 1-1 deadlock.

Reddick and Yuli Gurriel delivered run-scoring hits in the fourth inning to provide Astros right-hander Charlie Morton (10-5) with a working margin.

Morton surrendered one run in 6 1/3 innings, posting nine strikeouts against four walks while allowing three hits.

"I threw a couple of (four-seam fastballs), and I could see that they were a little late and that could be an approach thing, a scouting-report thing, it could be a bunch of things," Morton said. "But if it's working, it's working, so I threw it."

Walker labored through his five innings, waiting until his final inning to retire the side without allowing a baserunner.

A double-play grounder from Altuve helped Walker escape the first inning unscathed, but he surrendered three baserunners plus a run in the second, five baserunners and two runs in the third, and three more baserunners and two runs in the fourth.

While a fielding error by second baseman Brandon Drury didn't help Walker's cause, he allowed nine hits and two walks during his 101-pitch outing. And his inability to close innings was his undoing, with the Astros scoring three of their five runs against him with two outs.

Two of the runs Walker yielded were unearned.

"I don't think it was a struggle to find anything," Walker said. "I made good pitches. It was one of those games that every ground ball hit found a hole.

"I didn't have my best fastball velocity. I felt like I was locating pitches and my off-speed pitches were pretty good. It was one of those games where everything they hit found a hole."

The Astros hold a 2-1 lead in the four-game, home-and-home series that concludes Thursday at Minute Maid Park.

NOTES: Diamondbacks OF David Peralta is expected to rejoin the starting lineup Thursday after reinstatement from the paternity list. Peralta traveled from Phoenix to Houston on Wednesday night. ... Astros RHP Will Harris threw a bullpen session and is scheduled to face hitters Friday, the next step in his rehab for right shoulder inflammation. Harris has been on the disabled list since July 11. ... Diamondbacks LHP Robbie Ray is scheduled to work five innings or 75 pitches in a rehab start Thursday night for high Class A Visalia. Ray was placed on the seven-day concussion disabled list on July 28 after being struck in the head by a line drive on July 27. ... Astros C Evan Gattis participated in batting practice for the first time since landing on the concussion DL on Aug. 5.