Updated

For the second straight game, one of the Seattle Mariners' most consistent starters was victimized in the fourth inning — by the same Oakland hitter.

George Kottaras homered for the second straight game Saturday night and the Athletics went on to a 6-1 victory over the Mariners. Kottaras hit a two-run shot off Hisashi Iwakuma (6-4) in Oakland's four-run fourth.

It came one night after Kottaras hit a three-run shot of staff ace Felix Hernandez in a three-run fourth, also a 6-1 victory.

"Tonight's game was very similar to (Friday's) game," Mariners manager Eric Wedge said. "Disappointing to say the least. Oakland's a good ball club. They've been the best baseball club in the second half and we're going to have to come out and play better to beat them, as simple as that."

Iwakuma came into the game 5-1 with a 1.57 ERA in his previous seven starts, including 3-1 with a 2.05 ERA in five August starts. Before Friday, Hernandez was 9-1 with a 1.62 ERA in his previous 15 starts since June 17, with five shutouts including a perfect game.

The A's kept pace in the AL West with the Texas Rangers, who beat Tampa Bay 4-2. Oakland trails the Rangers by 4½ games and are in a virtual tie with the Yankees and Orioles atop the wild-card race.

Brett Anderson (4-0), who won his fourth straight start since recovering from Tommy John surgery, tamed the Mariners Saturday. He allowed one unearned run and six hits while striking out four in six innings. He lowered his ERA to 0.69. He has 19 strikeouts in his four starts.

"I think it's been more than we could ever expect," A's manager Bob Melvin said of Anderson's recovery. "To sit here and say he's 4-0 at this point coming off that is pretty terrific."

Mariners shortstop Brendan Ryan said Anderson, "has a live arm, pretty good slider, pretty good breaking ball, pretty sharp. When he establishes the fastball, it makes his slider even better, and it's already a 'plus' one."

Seattle finished 0 for 7 with runners in scoring position.

"I always hold myself to a high standard. You have to in this game, otherwise the game's going to beat you up," Anderson said. "Today was my most grinding start so far. It seemed like it was first and second one out every inning.

Anderson and Kottaras, acquired July 29 in a trade with Milwaukee, have had significant roles in helping the A's win 17 of their last 22 games. Their 78 wins are also four more than all of last season.

Kottaras has had 16 RBIs in his 13 games with Oakland — 13 in the last five games. With the Brewers, he drove in just 12 runs in 58 games.

With the score tied 1-1, Yoenis Cespedes opened Oakland's fourth with a double into the left-field corner. With one out, he stole third on a 1-0 pitch to Stephen Drew, who followed with a RBI single against the drawn-in infield. The ball just tipped off the glove of second baseman Dustin Ackley.

Kottaras then hit a 1-1 slider from Iwakuma for a two-run, line shot into the right-field seats to make it 4-1. It was his fifth home run of the season and the first time he hit a home run in consecutive games.

"Iwakuma has been pitching lights out," Melvin said. "He's been giving up two runs or less just about every game so he's been on a roll. For us to score some runs early again off of him was pretty impressive as it was off Felix."

Iwakuma, who worked 3 2-3 innings, allowing four earned runs and six hits, said through an interpreter that the slider Kottaras hit "was kind of a cookie, kind of easy to get a home run. I need to concentrate on that pitch."

Wedge said Iwakuma's pitches "flattened out that one inning. He left some pitches up and over, made a couple pitches he probably shouldn't have had — pitch selection-wise — so it happened quick."

Drew had an RBI single and Coco Crisp had a run scoring double after Kottaras' homer that gave them a 5-1 lead.

The A's forced Iwakuma to throw 25 pitches in the first inning and scored a run without a hit.

Crisp opened with an eight-pitch walk. He was forced at second on Josh Reddick's grounder. Cespedes followed with a two-out, one-hopper past third baseman Kyle Seager and into the left-field corner. It was ruled a two-base error, scoring Reddick.

The Mariners tied it in the second. Michael Saunders bounced a one-out double over the center-field wall. Miguel Olivo reached when shortstop Drew booted his ground ball, advancing Saunders to third. He came home on Trayvon Robinson's force-out.