CLEVELAND -- Jarrod Parker pitched into the sixth inning and Oakland hit four home runs, leading the Athletics to their sixth straight win, a 12-7 victory over the free-falling Cleveland Indians on Thursday and a sweep of the four-game series.Oakland, which has won eight of nine, maintained its one-game lead over Baltimore for the top spot in the AL wild card race. George Kottaras' three-run double broke a 1-1 tie in the fourth while Coco Crisp, Cliff Pennington, Josh Reddick and Josh Donaldson homered.While the Athletics are flying high, the Indians continue to fade. Cleveland has lost five straight, 14 of 15 and is 5-27 since July 27.Questions about manager Manny Acta's job security increase with every loss. Owner Paul Dolan said before the current homestand began last week that he had no immediate plans to fire the second-year manager, but the Indians have gone 1-6 since and show no signs their slide is going to end any time soon.Parker (9-7) gave up a leadoff home run to Jason Kipnis to start the game, but his teammates teed off on Cleveland starter Justin Masterson. The right-hander (10-12) has stopped losing streaks of 11 and nine games this month, but on Thursday he allowed eight runs, including three homers, in four innings. Masterson was pulled after the first three batters in the fifth reached base.Kottaras and Reddick drove in three runs apiece. Reddick had three hits while Crisp, Pennington and Yoenis Cespedes had two apiece.Crisp's two-out homer in the third tied the game. Cespedes' single and walks to Seth Smith and Josh Donaldson loaded the bases in the fourth. Kottaras, batting .148, scored all three runners with a drive up the gap to right-center. Pennington followed with a two-run homer.Stephen Drew started the fifth with a single and scored on Reddick's homer to right. Masterson was pulled after Cespedes' single.Donaldson hit a solo home run in the ninth.Parker has won his last two decisions after losing three straight starts. He pitched eight shutout innings against the Indians on Aug. 19 in Oakland.Masterson continued to struggle against the Athletics. The right-hander is 1-5 with a 10.36 ERA in six career starts versus Oakland.Asdrubal Cabrera and Carlos Santana managed to play the entire game, but even that couldn't help the Indians. Both had short nights Wednesday as Cabrera was ejected for arguing in the first while manager Acta benched Santana for not running out a ground ball.Cleveland pitching coach Ruben Niebla was ejected in the seventh inning by plate umpire Paul Emmel. Niebla went to the mound after Tony Sipp walked the bases loaded. Emmel broke up the conversation and kicked Nielba out after the two exchanged words. The argument continued at home plate and Acta stood between Niebla and Emmel.The Indians' losing ways have shown up in the attendance. The sparse crowd of 14,500 on Thursday was quiet for most of the game and players could be clearly heard as they called for popups. One frustrated fan taped empty bags to several seats near him. The biggest noise of the day came from the Blue Angels jets flying over Progressive Field as they prepared for this weekend's air show at the lakefront airport.NOTES: According to STATS LLC, the Houston Astros were 5-27 from July 20-Aug. 23 this season. Manager Brad Mills was fired on Aug. 18. ... Oakland is 61-35 with Cespedes in the lineup. ... The Athletics return home to begin a six-game homestand against Boston and Los Angeles. RHP Brandon McCarthy (7-5) faces RHP Aaron Cook (3-7) in the opener of a three-game set on Friday. ... RHP Chris Perez pitched the ninth for the Indians. Cleveland's closer hadn't pitched since Aug. 25 when he recorded a save against the Yankees in Cleveland's last win. ... The Indians are 5-9 at Progressive Field since Aug. 6. ... Cleveland starts a three-game home series with Texas on Friday. RHP Ubaldo Jimenez (9-13) meets RHP Ryan Dempster (9-6).