SEATTLE - In his first outing, Justin Masterson couldn't strike out anyone. But on Saturday night, he had Seattle batters flailing at pitches.

Either way is working just fine. Masterson and the Cleveland Indians are on an early tear.

Masterson took a shutout into the seventh inning, striking out nine, and the Indians benefited from one major defensive lapse by Seattle in a 2-1 win over the Mariners.

The Indians won their sixth straight and stand alone in first place in the AL Central for the first time since May 2008.

"It's going to come and go," Masterson said of his strikeouts. "Like anyone, you're going to get to a point where you say, 'I'm going to strike this guy out' and other times guys are putting it in play early, so I'll take that. I feel like with the stuff I have, I have the ability to go both ways at times."

Masterson (2-0) backed up an impressive season debut last Sunday against the Chicago White Sox with a performance that left Mariners batters waving at air most of the night. He gave up one run and four hits in 6 1/3 innings before turning things over to the bullpen.

His slider had late break. His sinker left Seattle batters either swinging over the pitch or grounding out weakly. And when he needed it, Masterson was able to reach back and throw into the upper 90s (mph) with his fastball.

Cleveland manager Manny Acta was right when he called Masterson's stuff "filthy."

"He threw a very good fastball with his usual movement and he was able to just pound the strike zone the whole night," Acta said. "Also, he had a very good slider. He had the lefties and righties swinging over it. He did a great job."

Masterson, who pitches from a unique arm angle, had Seattle hitters guessing for much of the night. Masterson had seven strikeouts in the first four innings and retired 13 of his first 15 batters before giving up a one-out double to Adam Kennedy in the fifth.

Masterson walked only one and nearly matched his season debut against the White Sox when he threw seven innings, giving up just one run but without any strikeouts.

The nine strikeouts against Seattle tied for the second-most in his career.

Rafael Perez and Tony Sipp worked the seventh and eighth in relief for Cleveland. Chris Perez pitched the ninth for his third save of the season and 13th straight dating to last August.

"This is fun. Everybody is loose. You start a season off like this, especially with a young team, it just gives us confidence," Perez said. "That's a dangerous combination with a young team, is confidence."

Cleveland got its only runs in the fourth, when Seattle made a defensive mistake the offensively challenged Mariners can't afford. Seattle starter Doug Fister gave up consecutive singles to Asdrubal Cabrera and Shin-Soo Choo to start the inning, then loaded the bases on a one-out intentional walk to Travis Hafner.

Orlando Cabrera hit a sacrifice fly that was deep enough to easily score Asdrubal Cabrera. Milton Bradley caught the fly and threw to third base in an attempt to keep Choo at second. The problem? No one was covering third for the Mariners. The ball bounced free and in his attempt to back up the play, Fister kicked the ball into the Indians dugout.

Choo was awarded home and Bradley was charged with an error for what proved to be the decisive run.

"We just messed it up. We didn't have a guy there," Seattle manager Eric Wedge said, noting that shortstop Brendan Ryan should have been at third.

That was all the offense the Indians got, but it was enough against a Mariners lineup that hasn't been able to come through with clutch hitting. The Mariners were 1 for 11 with runners in scoring position and haven't led since the second inning of last Sunday's loss at Oakland.

Michael Saunders had the one hit, an RBI single that scored Justin Smoak in the seventh, but Seattle failed to get Chone Figgins home following a leadoff double in the eighth.