Baek's status has been up in the air since Thursday when the team, short of long-relief pitching, designated him for assignment after he'd pitched both Nat 20 and May 21 in Detroit.

The Mariners had 10 days to trade him, release him or move him to the minor leagues, and Seattle opted to trade him and bring Wells into the organization.

A starter before this year, Baek had been up-and-down while working as the long man in the Seattle bullpen this season in nine of his 10 appearances.

He had a 5.40 ERA at the time of being designated.

Wells had nine saves with Portland, and in his big-league debut this week, he has a 6.00 ERA in two games with San Diego.

MARINERS 4, RED SOX 3: Jose Lopez gave the Mariners their first win in a week when he delivered a game-winning single down the left field line with two out in the ninth.

Lopez's hit shot past third baseman Mike Lowell, who never had a chance on the ball, and Wladimir Balentien raced home to end a seven-game Seattle losing streak.

Balentien had opened the inning with a single against Mike Timlin, then took second on a bunt by Miguel Cairo. A grounder from pinch hitter Jeremy Reed moved Balentien to third, and Ichiro Suzuki was intentionally walked before Lopez came to the plate.

Ichiro moved to second base on defensive indifference before Lopez beat Timlin with his single down the line. The ball would have been a double under normal circumstances, but once Balentien came home and Lopez got to first, the game was over.