OAKLAND, Calif. — The last time the Yankees flew out to the West Coast to begin a road trip, they immediately had a 10-run outburst against the Mariners.

Of course, those were simpler times, when they were still able to write Aaron Judge into their lineup instead of thinking about his toe.

On Tuesday, despite coming off a winning homestand and opening a series against the worst team in baseball, the Yankees fell flat in a 2-1 loss to the Athletics in front of 13,050 at Oakland Coliseum.

Jhony Brito pitched well in his second start back in the majors, but did not receive enough run support from his offense that has largely struggled in the month of June without Judge — even against the lowly Athletics (21-60), who squeaked out a win for just the second time in their last 12 games.

“This is grind time. We gotta get some guys going,” manager Aaron Boone said. “We’re all part of that. We know we have a higher standard and expect more and know we’re going to be better. But we’re going through it right now a little bit.”

The Yankees (43-36) recorded seven hits off right-hander Paul Blackburn and the Athletics bullpen, but stranded four runners over the final two innings.

One of those hits was a home run from Josh Donaldson in his first start since being benched for three straight games over the weekend, but it came with nobody on base in the fifth inning.

In the eighth inning, the Yankees had a chance to strike when Trevor May walked DJ LeMahieu and Anthony Rizzo on four pitches each and then fell behind 3-0 to Giancarlo Stanton with two outs.

But Stanton took a called strike and fouled off two pitches before hitting a chopper to third base to end the threat.

Stanton was unable to carry over any momentum from Sunday, when he chipped in an RBI single to the Yankees’ series-clinching win over the Rangers. Instead, he fell to 7-for-62 since returning from the IL on June 2.

“He’s working to get there,” Boone said.

Then in the ninth, Gleyber Torres led off with a pinch-hit single before Donaldson struck out looking and Billy McKinney flew out.

Anthony Volpe extended the inning with an infield single but left-hander Sam Moll struck out Kyle Higashioka to end the game.

“There’s no running away from anything,” said Volpe, who went 3-for-4 with three singles but was caught stealing second base in the seventh inning after going 15-for-15 to start his big league career. “We’re going to show up [Wednesday] and compete and prepare the way we know how to. I don’t think anyone’s faith is shaken at all, despite the results.”

It was the second straight quality outing from Brito since he was called up from Triple-A last week to help fill the rotation spot left open by Nestor Cortes’ shoulder injury.

After throwing 5 ²/₃ scoreless innings against the Mariners, Brito followed up with 5 ²/₃ innings of two-run ball against the Athletics.

The only damage was a triple by ex-Yankee Tyler Wade, who came around to score in the third inning, and then a solo home run by Seth Brown in the fourth.

“After being called up, I’ve had a really good staff, really good people here helping me to keep developing,” Brito said through an interpreter. “One of the things they mentioned to me early was to have the ability to get ahead in the count early and then try to figure out what pitch would be next to put away guys. I think I’ve been able to do that.”

But Brito was stuck with the loss after the Yankees were unable to mount much against the Athletics, leaving eight men on base and going 0-for-5 with runners in scoring position.

“We had a couple chances, but again, just not creating enough opportunities for ourselves to break through,” Boone said. “We gotta get a little more consistent.”