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SEATTLE -- After four months of making the trade deadline a challenge for Seattle general manager Jack Zduriencik, a weekend of getting routed may finally have the surprising Mariners accepting their fate.

And the Mariners have the Cleveland Indians to thank for potentially knocking them out of contention.

Grady Sizemore got it started with the 20th leadoff homer of his career, Jhonny Peralta hit his second career grand slam and the Indians hit four long balls in a 12-3 win over the Mariners on Sunday to complete a three-game sweep.

Seattle entered the weekend with optimism about its chances in both the AL West and wild-card races after a 5-2 road trip after the All-Star break. That optimism crumbled underneath an offensive onslaught by an Indians squad with the second-worst record in the American League.

It left the Mariners clubhouse almost silent after Sunday's blowout and had veterans wondering if some of their teammates would still be around when Friday's nonwaiver trade deadline arrives.

"After the game when there is dead time you look over at [Jarrod Washburn's] locker and you wonder if you're going to see him again. That's just the reality of the game" Seattle's Mike Sweeney said. "We have one of the best pitchers in the game that is going to be a free agent and there is probably a handful, if not a dozen teams that would like to have a guy like [Washburn] down the stretch.

"Ultimately the future is in our hands. We come out tomorrow and play good ball who knows what will happen."

At a time when Seattle needed to be playing its best to keep up with the streaking Angels in the AL West and a handful of teams in the wild-card race, the Mariners were taking steps backward that could push them toward "seller" mode as the trade deadline approaches.

Washburn is the gem of Seattle's offering, but slugging first baseman Russell Branyan might be available as well. Erik Bedard was considered available, but landed on the disabled list for the second time this season on Sunday with inflammation in his shoulder. He still could be an option for other teams after July 31 if he clears waivers.

All three are free agents after the season.

"We hope we can keep this team together when July 31 rolls around," Sweeney said.

Cleveland arrived in Seattle complaining about its lack of offense and extra-base hits. They left after hitting 11 homers, scoring 31 runs, collecting 39 hits and sweeping the Mariners in Seattle for the first time in 11 years.

They are dealing with the trade debate themselves. Reigning AL Cy Young winner Cliff Lee won his third straight decision on Sunday, yet continues to be linked with trade rumors from one coast to the other.

"It's kind of pointless to waste time thinking about it because I have zero control over it," Lee said after improving to 7-9 on the season. "Now I'm an Indian and that's where my focus is."

Seattle entered the weekend seven games over .500 mostly because of a pitching staff that has made up for a light-hitting offense all season. Those arms took a beating during a warm weekend where the myth of Safeco Field being unfriendly to the long ball was debunked by the Indians.

Facing its eighth straight lefty starter in Seattle's Jason Vargas, Sizemore lined the sixth pitch of the game into the right field seats for his 14th homer of the season. Peralta broke the game open with his grand slam in the fifth that greeted reliever Shawn Kelley. It was Peralta's seventh homer this season and first since July 8. And Travis Hafner and Ben Francisco added back-to-back shots in the sixth off Miguel Batista that brought a cascade of boos.

About the only positive from Sunday was Seattle didn't lose any more ground in the AL West (7½ back of the Angels) or the wild card (6½ behind Boston).

Lee (7-9) gave up a pair of first-inning runs on Franklin Gutierrez's two-out single before retiring the next 13 straight. He gave up just six hits and two runs, while striking out four.

Game notes

Seattle LF Michael Saunders picked up his first major league hit in the seventh and added an RBI single in the ninth. ... Peralta's other grand slam came in 2006 against Tampa Bay. ... Cleveland is scheduled to face its ninth straight lefty starter on Monday in the Angels' Joe Saunders. According to STATS, it'll be the first time in Indians' history that has happened since at least 1919.