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Indians manager Manny Acta has been in professional baseball since 1986. He thought he had seen it all.

Thursday's 12-7 loss to Oakland extended the Indians' latest losing streak to five in a row and was their 14th defeat in 15 games. Cleveland also is 5-23 in August — putting it one loss away from the franchise record of 24 in a month (set in July 1914) — and a major-league worst 5-27 since July 27.

Acta, in his third season with the Indians after managing the Washington Nationals from 2007-2009, is at a loss to explain why his team has fallen so quickly.

"I've never been through a month like this anywhere," he said. "Not in Washington, the minor leagues or winter ball, either as a coach or a manager."

Acta has tried everything to turn his team around. Prior to Wednesday's game, he divided his players into two teams for a spirited batting practice contest in which the losers had to pick up several dozen baseballs that were hit into the outfield. Acta also benched catcher Carlos Santana for not running out a ground ball during the game.

"We're making it clear to everyone that they need to take care of their own business," he said. "One person isn't going to get us out of this situation. Everyone needs to go out and do their job to the best of their ability."

According to STATS LLC, the Indians have now matched the least successful 32-game stretch in the majors this season. Houston went 5-27 between July 20 and Aug. 23, firing manager Brad Mills on Aug. 18.

Questions about Acta's job security have increased with every loss, even though Indians owner Paul Dolan said last week that he had no immediate plans to dismiss him. Dolan made that statement at the start of Cleveland's ongoing 1-6 homestand.

"It's not the manager's fault," Indians shortstop Asdrubal Cabrera said. "We're playing bad right now. He's not on the field with us. We don't want anybody to lose his job. We've got to be together."

Cleveland second baseman Jason Kipnis, who started the afternoon on a high note with his second career leadoff homer, also said the players were to blame.

"We're still looking for the offense, defense and pitching to get going all at once," he said. "Once that happens, the wins will start to come."

Justin Masterson, who had stopped the Indians' 11- and nine-game losing streaks this month, allowed eight runs in four-plus innings. The right-hander (10-12) gave up home runs to Coco Crisp, Cliff Pennington and Josh Reddick, and also surrendered a three-run double to George Kottaras, who was hitting .148.

In six career starts against Oakland, Masterson is 1-5 with a 10.36 ERA.

"I just don't know, it's crazy," Masterson said of his struggles against the Athletics. "I'm sure there could be some scientifical analysis we could do out there. I'd be happy just to win some ballgames, that's about it."

The Athletics tacked on four runs against relievers Chris Seddon, Tony Sipp and Chris Perez en route to sweeping the four-game series. Josh Donaldson completed their four-homer assault with a leadoff shot off Indians closer Perez.

Cleveland pitching coach Ruben Niebla was ejected in the seventh for arguing balls and strikes by home plate umpire Paul Emmel.

One day earlier, Cabrera was tossed for the same reason by home plate umpire Gary Darling.

Right-hander Jarrod Parker (9-7) earned the victory despite giving up five runs and eight hits in five-plus innings for Oakland, which maintained its one-game lead over Baltimore in the AL wild card race.

Shin-Soo Choo, who drove in three runs, was struck on the outside of the right knee by Jim Miller's pitch in the eighth, but remained in the game.

A quiet crowd of 14,500 was on hand for the 12:05 p.m. first pitch. Players could clearly be heard calling for popups, while one frustrated fan taped empty bags to several seats near him.

The biggest noise throughout the game came from the Blue Angels jets flying over the park, practicing their routines for the annual air show at the lakefront airport.

NOTES: The Indians have lost eight straight games to the Athletics. ... Santana vowed to run the bases harder after Acta removed him Wednesday. "It won't happen again," Santana said. "He's the manager. He made the decision. I respect that." ... Indians closer Perez made his first appearance since Aug. 25, pitching the ninth inning. ... Cleveland hosts Texas to open a three-game series Friday at 7:05 p.m. RHP Ubaldo Jimenez (9-13) faces Rangers RHP Ryan Dempster (8-6).