OAKLAND -- Right-hander Yonny Chirinos did his part to end a recent skid that has seen the Rays fall further behind the first-place New York Yankees than they have been all season.

But the offense struggled again, and reliever Diego Castillo had his second bad outing in a row. The result was a 4-2 loss to the Oakland A's that sent Tampa Bay to its ninth loss in its past 12 games.

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Chirinos, whose seven wins this season are one behind team leader Charlie Morton, allowed two runs on six hits in six innings. It was his fourth quality start in a row. But Chirinos was lifted after throwing 88 pitches, his fewest since May 27, when he was pulled after five no-hit innings and 69 pitches in an 8-3 win against Toronto.

Castillo took over for Chirinos to start the seventh and allowed the first four A's hitters to reach base. Beau Taylor drew a leadoff walk, Marcus Semien singled and Matt Chapman doubled home a run to snap a 2-2 tie. Matt Olson was intentionally walked to load the bases, then after an out, Castillo hit Ramon Laureano to force home the A's second run of the inning.

Castillo was touched for four runs in two-thirds of an inning Thursday night during a 5-4 loss to Oakland.

The Rays had just tied the score 2-2 in the top of the seventh on a two-out homer by Ji-Man Choi, his ninth of the season. Chirinos was prepared to go out for the seventh, especially after throwing at least 91 pitches in each of his past four starts.

"I didn't have that many pitches," Chirinos said through an interpreter. "I was prepared to be out there, but that's the manager's decision."

Chirinos had his longest outing this season on June 7, when he threw eight shutout innings and 101 pitches in a 5-1 win against the Boston Red Sox. The Rays still have a 2 1/2-game lead over the Red Sox in the American League East after Boston lost on Saturday. But the Red Sox have been gaining ground on Tampa Bay, while the division-leading Yankees have been pulling further ahead.

Manager Kevin Cash was asked if fatigue might be playing a role in the Rays' June swoon.

"I don't think this is a tired group," Cash said. "We're just not getting it done."

Catcher Mike Zunino said inexperience might be a bigger factor than fatigue.

"One bad outing can snowball into another," Zunino said. "People forget how young some of the pitchers are here. It's a learning experience."

Castillo and Chirinos are 25. They are both in their second seasons after solid rookie campaigns.

Pitching, however, isn't the only problem right now. The offense isn't doing much, either. In the nine losses over the past 12 games, Tampa Bay has scored a total of 21 runs. The Rays haven't topped four runs in any of the defeats.

"Everybody's guilty," Zunino said. "We've got hitters trying to get six hits back in one at-bat. Every team goes through stretches like this. But we're sitting here in June. I'd rather take our bumps and bruises now and come back strong after the [All-Star] break."

The Rays had their share of scoring opportunities against A's starter Mike Fiers and three relievers. Between the second and seventh, the Rays had baserunners in every inning. In four of those innings, they left runners stranded in scoring position.

The biggest letdown might have occurred after Choi's game-tying homer. Slumping Austin Meadows followed with a triple when Oakland right fielder Stephen Piscotty dived for his sinking liner and missed. The ball rolled all the way to the fence as Meadows raced around the bases. But he was given the stop sign at third rather than risk scoring against Piscotty, who has an above-average arm.

"Definitely when I hit the home run, the atmosphere came back," Choi said through an interpreter.

It went away quickly, as the A's needed only three batters to get the lead back in the bottom of the seventh.