Heading into the season, the Yankees knew the Blue Jays might be the toughest test they’d face in what figures to be a hard-fought battle in the AL East. 

They got their first dose of it Monday, and after two straight wins to open the season against the Red Sox, the Yankees lost a second consecutive game, this time 3-0 to Toronto. 

“You have to be on your game to shut this lineup out,’’ said Jameson Taillon, admiring the work of his counterpart, Alek Manoah. “It’s not gonna happen much this year, I don’t think.” 

The Yankees got just one hit in Manoah’s six innings and four for the game, while the Blue Jays turned a pair of key double plays to thwart rallies. 

“They’re gonna be tough all year,’’ Aaron Judge said. 

And it was Judge who ended up hearing boos when he whiffed for the second out of the eighth inning. 

The outfielder, who turned down the Yankees’ seven-year, $213.5 million contract extension prior to Opening Day, wasn’t bothered by the smattering of boos from the announced crowd of 26,211. 

“It’s not rare,’’ Judge said of the reaction. “I’ve been hearing it since [my rookie year of] ’16. It’s nothing new.” 

Perhaps it’s not new, but it’s fairly rare. 

Aaron Boone noted the smaller crowd and the fact none of the Yankees did much to make the crowd cheer. 

“Coming off a big weekend series, a Monday crowd, you tend to hear those things,’’ the manager said. “That sometimes goes with playing. I’m not worried about it. [Judge] has got plenty of support out there.” 

On this night, Taillon did not. 

In his first start of the season and first since offseason ankle tendon surgery, the right-hander was strong over five innings, striking out six, but he made a mistake to George Springer in the third. 

It was the Blue Jays’ fifth straight win in The Bronx. 

Manoah — who tossed six scoreless innings at the Stadium last May 27 in his MLB debut — was just as impressive on Monday night. 

And Springer, the former Astro — booed throughout the night — led off the game with a line-drive single to left. 

Taillon pitched ahead to nearly every batter in the early going and retired seven straight after Springer’s single. 

Santiago Espinal then reached on a single with one out in the third before Springer came up again and this time sent a laser into the left-field seats to give the Blue Jays a 2-0 lead. 

Taillon said the homer came off a slide-step pitch, something he’s working on to stop base runners from stealing on him. 

Manoah walked the bases loaded with two out in the bottom of the inning before Giancarlo Stanton came up and grounded one into the hole beyond shortstop, but Bo Bichette made a terrific back-handed play and a strong throw to get Stanton at first. 

While Manoah occasionally struggled with his command, the Yankees weren’t able to get much hard contact against the right-hander. 

“He’s had our number to this point,’’ Boone said. 

Toronto added a run off Michael King in the seventh with a two-out single by Espinal and an RBI double to the fence in right-center by Springer, for his third RBI of the night. 

Gleyber Torres greeted Trevor Richards with a single to left in the seventh and Aaron Hicks followed with a walk. Kyle Higashioka hit a flare to right, where Teoscar Hernandez made a nice sliding catch for the first out. 

Josh Donaldson pinch hit for Marwin Gonzalez and hit a hard grounder up the middle, but second baseman Espinal, shifted toward the base, made a terrific grab to his left, turned and made a perfect throw to Bichette, whose strong throw to first completed the inning-ending double play. 

Gallo led off the bottom of the ninth with a single, but Torres followed with a hard-hit double play, ending any hope of a comeback. 

It continued Toronto’s mastery over the Yankees at the Stadium, where the Jays swept a four-game series in September and won eight of the 10 meetings between the two teams here last year.