SEATTLE -- For whatever reason, Houston Astros starter Dallas Keuchel couldn't get a grip on the baseball during the first inning on Saturday night but was able to get through it without any damage.

The second inning was a much different story. After Keuchel's command went awry, leading to his worst outing of the season, the Astros fell 6-3 to the Seattle Mariners and might be losing their grip on the American League West.

Houston (40-30) dropped its second consecutive game and barely held on to its 2 1/2-game lead over Texas atop the division.

The Mariners hit three home runs off Keuchel, whose shaky second inning also resulted in two bases-loaded walks.

Keuchel (8-3) gave up season highs of five runs, four walks and three home runs. All four walks came in the second inning, and he walked in two runs to give up an early 2-0 lead.

"We don't see that very often out of him," Houston manager A.J. Hinch said. "I know he didn't feel the ball out of his hand; it was slippery. He had trouble gripping the ball."

Keuchel, who had allowed four home runs all season and had not given up three in a game since July 2013, refused to use the ball texture as an excuse.

"I can't walk four players in the second inning -- even if I can't get a grip on the ball," he said. "I've got to figure something out there."

Right fielder Nelson Cruz, left fielder Seth Smith and designated hitter Mark Trumbo each hit a solo homer off Keuchel to lift the Mariners (32-37) to their second consecutive win.

"In my mind, this was a big win for us," Seattle manager Lloyd McClendon said. "We needed to have it."

Seattle starter Taijuan Walker (5-6) gave up two solo homers but not much else in 6 1/3 innings. He allowed five hits and three runs while striking out 11.

Mariners starting pitchers had 21 strikeouts and no walks in the first two games of the series with Houston (40-30).

Keuchel struggled through one of his worst starts of the season. He walked in two runs in the second inning and gave up solo homers in the third and fifth as the Astros fell behind 4-2.

Cruz ended a 22-game streak without a homer by hitting a third-inning solo shot that gave the Mariners a 3-2 lead. Cruz's 19th home run of the season was his first since May 27.

Smith added a fifth-inning home run off Keuchel, then Trumbo went deep in the sixth.

"I just didn't get the job done," Keuchel said. "After getting spotted two runs early against a good pitcher, I've got to take advantage of that."

Designated hitter Evan Gattis and third baseman Luis Valbuena each homered for the Astros. Second baseman Marwin Gonzalez added an RBI single in the seventh to close the gap to 5-3.

Seattle second baseman Robinson Cano got the run back with an RBI single in the bottom of the seventh.

Houston threatened again with back-to-back, one-out singles in the eighth, but Mariners fill-in closer Carson Smith came on and got Seattle out of that jam before pitching a scoreless ninth for his fifth save of the season.

Cruz and Trumbo, who were facing Keuchel for the first time as Mariners, have an impressive history against the Houston ace. After Saturday night's game, they are a combined 11 of 22 with four home runs against Keuchel.

Hinch was ejected in between the top and bottom of the sixth after he argued a fan-interference call with third-base umpire Mike DiMuro.

Hinch was upset that the Mariners were awarded the third out of the inning when a Seattle fan reached out for a fly ball in foul territory and kept Mariners shortstop Brad Miller from possibly making a spectacular catch.

The fan was removed from his seat shortly after Hinch was ejected.

"Every out matters," Hinch said when asked about his argument. "I felt they took one away from us. I don't understand how you can assume a catch when (Miller) is running full speed from shortstop, crashing into a wall.

"A fan interferes and (the umpires) say: catch. ... I'm not sure why we wouldn't instruct all of our home fans to get in the way."

Houston jumped out to a 2-0 lead on solo home runs from Gattis and Valbuena in the top of the second.

Gattis led off the inning with a 340-foot shot that barely cleared the fence in right field. Valbuena's homer traveled 386 feet to right.

Six of Valbeuna's 17 home runs this season are against the Mariners.

All four of Houston's runs during the first 11 innings of the series came on solo homers.

Keuchel breezed through the first inning but lost his command in the bottom of the second. Four walks, including back-to-back free passes with the bases loaded to drive in two runs, helped the Mariners tie the score 2-2.

"Traditionally, (Keuchel) has been very tough on us," McClendon said. "I thought we out some decent at-bats against a pretty good pitcher."

After getting shut out four times in an eight-game span heading into the Houston series, Seattle has now scored five or more runs on back-to-back nights since April 19 and 20.

"I think it's coming," McClendon said. "I think there's a lot more to be had with this offense. The last two nights was certainly good to see."

NOTES: The Mariners announced a few hours before Saturday's game that hitting coach Howard Johnson had been reassigned within the organization. Former Mariners DH Edgar Martinez, now 52 years old after winning two American League batting titles with Seattle, was named as his replacement. Martinez's only experience as a coach is as a part-time roving hitting instructor at spring training. "I don't look at it as a new voice," Mariners general manager Jack Zduriencik said. "I look at it as a person who has a great degree of expertise." ... Houston 2B Jose Altuve (hamstring) was not in Saturday's lineup, marking the third day in a row he did not start. ... Astros starter Dallas Keuchel was facing Seattle for the first time this season after going 3-1 with a 2.17 ERA against the Mariners last year. ... Seattle RHP Hisashi Iwakuma, who has been on the disabled list since late April because of a strained latissimus dorsi muscle, made his first rehab start Saturday night. He pitched 3 2/3 innings for Class A Everett, throwing 56 pitches with three strikeouts and no walks. Iwakuma's next rehab start is likely to come at Triple-A Tacoma sometime this week.