CLEVELAND -- Yan Gomes hit a three-run homer in the 10th inning and the Cleveland Indians, twice revived by Seattle's fielding errors, beat the Mariners 10-8 on Monday to complete a four-game sweep.
Gomes, who also homered in the second, drove a 3-2 pitch from Charlie Furbush (0-3) over the wall in left, giving the Indians their fifth straight win, third walk-off over the Mariners in four days and most improbable victory of what is becoming a special season.
As Gomes reached the plate, he was mobbed by teammates following the comeback that became necessary after Cleveland's bullpen gave up homers in the eighth, ninth and 10th innings.
It was the Indians' first four-game sweep of Seattle since 1981, and the rally gave Cleveland its 18th win in 22 games.
Joe Smith (2-0) won despite giving up a go-ahead homer to Justin Smoak in the 10th.
Ryan Raburn hit a three-run homer for Cleveland, which opened a 2 1-2 game lead over Detroit in the AL Central.
The Mariners got a tying homer by Kyle Seager in the eighth and a go-ahead shot by pinch-hitter Endy Chavez in the ninth but couldn't close it out because of their own miscues.
The Indians were an out away from losing in the ninth when Seattle closer Tom Wilhelmsen dropped an underhanded toss while covering first, allowing the Indians to tie it 7-7.
After Smoak homered in the 10th, the Indians were three outs away from losing when the Mariners helped them again.
Michael Brantley singled and Drew Stubbs followed with a bunt that Furbush, seeking his first career save, fielded but bobbled. The left-hander rushed his throw to first and would have had Stubbs -- umpire Tim Timmons called him out -- but Smoak dropped the ball.
Gomes then delivered his game-winning homer as the Indians improved to 21-7 since April 20.
The final three innings bordered on the absurd as the Mariners took the lead only to give it away with their bone-headed plays.
Wilhelmsen's error in the ninth not only cost the Mariners a certain win, but it allowed Cleveland closer Chris Perez to escape a loss after he gave up the homer to Chavez in the ninth. It was another bad outing for Perez, who gave up back-to-back homers in the ninth on Saturday but wound up getting a win.
With Seattle trailing 6-5 in the eighth, Seager homered off Vinnie Pestano, who recently came off the disabled list, into the Mariners' bullpen for his fifth homer.
The Indians took a 6-5 lead in the seventh off Yoervis Medina without hitting the ball beyond the infield grass.
Seattle starter Hisashi Iwakuma was tagged by the Indians for five runs in four innings, but the right-hander settled in and retired the final seven hitters he faced and got a no-decision. He gave up seven hits and struck out six in six innings.
Iwakuma won his previous three starts and came in with the AL's second-lowest ERA.
Indians starter Scott Kazmir didn't get out of the fourth as the teams combined for 10 runs and 14 hits through four innings before the game slowed to a crawl.
Raburn and Gomes hit back-to-back, two-out homers in the second, when the Indians caught a break to take a 4-2 lead.
With Carlos Santana on with a one-out double, Mark Reynolds just missed a homer, flying out to the track in left. Brantley walked and Raburn fell into an 0-2 hole and appeared to take strike three, but plate umpire Laz Diaz called Iwakuma's pitch a ball to give Raburn new life.
He made the most of it, connecting for his fifth homer to make it 3-2. Gomes followed with a shot onto the pedestrian porch in left.
The Mariners scored two in the third to tie it, with Morales hitting an RBI single and Kyle Seager scoring Michael Morse grounded into a double play.
Seattle, which entered the game just 1 of 23 with runners in scoring position in the series, made the most of their first two chances and took a 2-0 lead in the first -- their first one of the four-game series -- on an RBI double by Kendrys Morales and Morse's run-scoring single.
NOTES: Mariners SS Brendan Ryan started a gorgeous double play in the fourth when he one-hopped Bourn's liner and flipped the ball with his glove to 2B Robert Andino, who fired to first to nip Cleveland's speedy leadoff hitter. ... Indians RHP Brett Myers (elbow) will make his second rehab start on Wednesday at Double-A Akron. ... Frequent fliers, the Mariners will log 52,509 travel miles this season, most in the majors. ... Mariners RHP Aaron Harang will start Tuesday against the Angels. He missed his previous start with back stiffness. ... Indians RHP Justin Masterson was named the AL's pitcher of the week. He pitched 16 scoreless innings in wins over the Yankees and Mariners, allowing just seven hits and striking out 20.