With three of the majors' top five home run hitters on the field, a power outage seemed unlikely in the series opener between the Colorado Rockies and Seattle Mariners.

After an unlikely source provided a decisive homer, the Rockies will try to win three straight road games for the first time since late May on Saturday night at Safeco Field.

Colorado's Nolan Arenado and Carlos Gonzalez are engaged in a friendly fight for the NL home run crown. Arenado has a league-leading 38, while Gonzalez has 37.

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Arenado, who had homered in eight of his previous 11 games, went 1 for 5 in Friday's 4-2 win and is just 2 for 17 over his last four against the Mariners. Gonzalez has a MLB-high 24 homers since the All-Star break, but he went hitless to drop his average to .192 in 21 games versus Seattle.

While the big sluggers were kept in the yard, Dustin Garneau snapped a scoreless tie with a three-run homer that put the Rockies ahead in the seventh inning. His second home run in as many games also ended a streak of 24 1-3 scoreless innings by Seattle pitchers.

The rookie catcher is finally getting an opportunity after seven years in the minors with Michael McKenry and Nick Hundley sidelined due to injury.

"It was a little front-door cutter," said Garneau. "He got me my at-bat before where I popped out to the catcher. So, I took a chance and luckily I got my barrel to it."

Seattle's Nelson Cruz had homered in three straight games and nine of 16 at Safeco. The power surge moved him within one of Baltimore's Chris Davis for the MLB lead with a career high-tying 40 before he went 0 for 4 with two strikeouts in the opener.

Kyle Seager hit the team's lone home run in the eighth. He's batting .455 with six longballs and 16 RBIs over his last 14 and .393 with three homers in his previous seven versus Colorado.

"It was a pitch up and in the zone a little bit, something I could hit and fortunately it worked out," said Seager.

The Mariners (68-74) won five in a row to get within six games of the AL's second wild-card spot before dropping three of the first five on this 10-game homestand.

They'll try to get back on track behind Roenis Elias (4-8, 4.30 ERA), who has allowed one home run in four appearances since returning from a seven-week stint at Triple-A Tacoma.

The left-hander, who has never faced the NL West-worst Rockies, looks to snap a personal four-game losing streak after giving up two runs over 5 1-3 innings in Monday's 3-0 home loss to Texas.

Colorado (59-82), which ended a five-game skid versus Seattle, has gone 6-25 against left-handed starters.

Yohan Flande (3-2, 4.65) also has struggled with consistency since joining the Rockies' rotation in late July. He went 1-0 with a 2.70 ERA in his first two starts, but has a 5.63 mark over his last six.

The left-hander is looking to regroup after allowing a career-high six runs over 4 1-3 innings in Sunday's 7-4 home loss to San Francisco. He worked one scoreless inning of relief against the Mariners on Aug. 5 when he picked up the win in a 7-5 victory at Coors Field.

Seattle's Franklin Gutierrez could start for the first time in nine games due to a strained groin, while Colorado's Jose Reyes is expected back after sitting Friday with a tight Achilles.