DENVER -- The Colorado Rockies were swept for the second time at home and the third time overall this season. Going 2 for 16 with runners in scoring position certainly doesn't help.
Neither did the fact that Todd Helton struck out swinging on a 3-2 count with runners on second and third to end the game.
"On a fastball right down the middle," said Helton. "We're not playing well. You are going to put more pressure on yourself to do what you have to do to win some games."
Helton fanned to strand two other runners in the fifth inning. Catcher Wilin Rosario struck out twice and lined out softly leaving three runners in scoring position in a 0-for-4 game.
"We are in a rut," Colorado manager Jim Tracy said. "We have to get three or four guys, significant guys, going offensively. That's not what's taking place right now. Some of that is happening from our Nos. 4, 5 and 6 hitters, a very significant area of the lineup."
Jesus Montero and Justin Smoak hit back-to-back home runs, and Blake Beavan tied a season-high with seven strikeouts for the Mariners. Mike Carp also homered and Dustin Ackley had two hits.
Carlos Gonzalez homered among his three hits and Dexter Fowler also went deep for Colorado, which has lost four straight overall and eight of 10 at home in May.
"It's hard to see all the guys' struggles because it's never been that way," said Gonzalez. "You are going to have a couple of guys step up."
The Mariners were 8-4 on the road after sweeping a series in Detroit last month before losing 12 of their previous 13 away from home. Coors Field proved to be a cure for their struggles, but not without a tense ninth inning.
Leading 6-2, closer Brandon League came on and gave up a one-out, pinch-hit homer to Fowler, his fifth. Eric Young and pinch-hitter Jason Giambi followed with singles, and Gonzalez knocked in a run with a single to center.
Troy Tulowitzki hit a potential double-play ball to third, but Smoak bobbled the relay at first to keep the inning alive. League then struck out Helton to end the game.
Beavan (2-4) followed strong outings by Seattle's starters in the first two games with five-plus innings of two-run ball. He gave two runs and seven hits while walking one to get his first win since April 15.
Beavan's only mistakes were a two-out solo homer to Gonzalez and a two-out RBI single by Jordan Pacheco. He left after giving up a leadoff double to Michael Cuddyer in the sixth, but righty Shawn Kelley got Rosario to line out and struck out Pacheco and pinch-hitter Tyler Colvin.
Colorado's Jeremy Guthrie (2-2) allowed three homers in a game for the fifth time in his career.
"Three balls left the ballpark," said Tracy. "That's the difference in the game."
The Mariners jumped out to the early lead for the third straight game. Ackley led off the game with a double, moved to third on fly out and, after a walk to Kyle Seager, the two successfully completed a double steal to score the first run. Seager scored on Smoak's two-out single to make it 2-0.
Gonzalez cut the lead in half with his eighth home run in the bottom of the first before Seattle's big bats woke up.
With two outs in the third, Montero hit a two-run homer to left, his sixth, and Smoak followed with fifth homer into the front row of the right-field bleachers to make it 5-1.
Pacheco's RBI single in the fourth made it 5-2 but Carp's fourth homer off the second deck in right in sixth put Seattle ahead 6-2.
Guthrie left after giving up six earned runs, striking out seven and walking two in six innings.
NOTES: The Rockies recalled RHP Adam Ottavino from Triple-A and optioned LHP Rex Brothers. ... Mariners C Miguel Olivo will join Triple-A Tacoma in Iowa on Monday to begin a rehab assignment. Olivo has been on the DL since May 5 with a strained right groin. ... Mariners RHP Felix Hernandez will face Texas RHP Yu Darvish in the opener of a three-game series in Seattle on Monday. ... Colorado will send lefty Jamie Moyer against Marlins lefty Mark Buehrle in Miami on Monday.