OAKLAND, Calif. -- Scott Kazmir won 15 games and made the American League All-Star team last season, his first with the Oakland A's.

Kazmir set the bar high, but A's manager Bob Melvin said the left-hander outdid himself Thursday night, allowing just two hits over eight shutout innings in a 4-0 victory against the Seattle Mariners at the O.co Coliseum.

"We've seen some great games out of him," Melvin said. "That's the best I've seen him."

Kazmir (5-5) struck out seven, including four straight at one point, and was perfect until left fielder Franklin Gutierrez doubled with one out in the fifth. He didn't walk a batter. He improved to 5-0 against teams in the American League West.

"I felt like I was in control, I did, with every pitch," Kazmir said. "I was throwing the curveball for a strike, I was able to throw a curveball into the dirt when I needed to. That's something I haven't had the past couple of starts. Just having that changeup, being able to throw that off of a couple fastballs in the same spot, that was huge for me."

Kazmir is in the final year of his contract and already has dealt with trade rumors for weeks. He raised his value with Thursday's gem.

"I know he likes it here," Melvin said. "He's all about his team. He's become a leader here the last couple years, by performance and in the clubhouse. He's a resource for me. When you're that good, and we have the record that we do, there's going to be speculation and there's going to be guys talked about based on the fact they're in the last year of their contract."

The A's, who beat the Mariners for just the second time in seven meetings this season, scored all four runs on two-out hits. Catcher Josh Phegley had a two-run double in the first, shortstop Marcus Semien a solo home run in the fifth and rookie left fielder Mark Canha an RBI triple in the seventh, his first career triple.

Phegley said Kazmir didn't shake him off as often as usual because every pitch was working well.

"He was just on the corners of the plate the whole time," Phegley said. "He didn't really give them anything to hit, and I think it frustrated them a little bit and they started getting a little more aggressive and that's when we started throwing his changeup and his cutter down and they were just getting themselves out."

The Mariners posted back-to-back shutout victories against the San Diego Padres the previous two days, but the A's ended the 18-inning scoreless streak in the first.

Mariners left-hander Roenis Elias (4-6) gave up three runs and three hits over six innings, striking out seven and walking one.

"He gave us what he could, considering the first inning," Mariners manager Lloyd McClendon said of Elias. "The tough thing about the first inning is there were two outs, two strikes, no one on and he ends up giving up two runs. That cost him the ballgame."

Gutierrez went 2-for-3, getting both of Seattle's hits against Kazmir.

"He had all of his pitches going and was throwing 93-94 (mph)," McClendon said of Kazmir. "He kept us off balance."

A's right-hander Edward Mujica pitched a scoreless ninth.

After Elias retired the first two batters he faced in the first inning, A's second baseman Ben Zobrist walked and moved to third on designated hitter Billy Butler's double down the left field line. Phegley brought them both home with an opposite-field double down the right field line.

"He threw something I guess within a bat's reach, and I happened to put it on the chalk," Phegley said. "With two guys on and two outs in the first inning, that's just a good way to set the tone for the game."

The A's extended their lead to 3-0 on Semien's blast over the left field fence, his seventh homer of the season.

Melvin said Kazmir probably could have talked his way into pitching the ninth inning but didn't try.

"I thought that was enough," Kazmir said. "I was thinking about it. Just felt like that was probably a good time."

NOTES: Oakland RHP Sonny Gray rejoined his teammates Thursday after a three-day stay in a hospital for severe bacterial gastroenteritis caused by salmonella. Gray likely will miss his scheduled start Sunday, although an official decision has not been made. It is possible he also could miss his final scheduled start before the All-Star break. ... The Mariners called up SS Chris Taylor from Triple-A Tacoma and designated veteran INF/OF Willie Bloomquist for assignment. Bloomquist was batting .159 in 35 games this season. Taylor started against the A's and went 0-for-2. ... The A's acquired RHP Cody Martin from Atlanta in exchange for international bonus money and assigned him to Triple-A Nashville. Martin went 2-3 with a 5.40 ERA in 21 relief appearances this year with the Braves and also spent time at Triple-A Gwinnett. To clear a spot on the 40-man roster, Oakland designated Nashville 1B Nate Freiman for assignment.