TORONTO — Michael Pineda was not good in his first start of the season, but double-digit run support paved the way to victory. He pitched far better Wednesday night but received little backing from his offense in a 7-2 loss to the Blue Jays at Rogers Centre.

The Yankees (4-3), who came in averaging an AL-best 6.33 runs, had plenty of chances against lefthander J.A. Happ but mostly failed to get the big hit. That was par for the course down the stretch last season against lefthanders and the case the two times they’ve faced lefty starters this season.

“We’ve struggled a couple of times against the lefthanders this year,” Joe Girardi said. “I don’t think this will be a pattern.”

The Yankees went 1-for-7 with runners in scoring position against Happ in six innings, stranding seven. Happ (1-0) allowed one run, seven hits and three walks. He struck out four.

“It’s early in the season,” said Mark Teixeira, whose eighth-inning homer pulled the Yankees within 3-2 before Ivan Nova allowed four runs in the bottom of the inning. “I like our lineup against lefties. You look at lineup tonight, it’s a lineup that’s going to score runs. It didn’t happen tonight but we’ll score runs.”

One bat that could help belongs to Alex Rodriguez, off to a slow start. A-Rod, 40, went 0-for-4 and is hitting .136.

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“I think he’s looked fine,” Girardi said. “Older guys can take a little while to get going. That doesn’t really concern me. I thought he just missed a couple of balls tonight.”

Pineda (1-1), who allowed six runs in five innings in a 16-6 victory over the Astros on April 6, allowed three runs (two earned) and five hits in six innings against the Blue Jays (4-5). He walked three and, mostly because of a biting slider, struck out six.

Teixeira’s third homer, off Drew Storen, was a shot off the foul netting in right. Then Nova, who lost the battle for the fifth starter’s job to CC Sabathia, failed in his second relief appearance of the season. “We need him to be able to get us outs,” Girardi said.

Switch pitcher Pat Venditte, a former Yankee called up earlier in the day, pitched a 1-2-3 ninth.

The Blue Jays took a 1-0 lead in the second when the No. 9 hitter, Ryan Goins, hit the first of his two doubles, driving former Yankee Russell Martin. Goins went 3-for-4 with two doubles and two RBIs.

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Ronald Torreyes, starting at short for Didi Gregorius, led off the fifth with a double, giving him a 6-for-7 start. Austin Romine smacked a single up the middle to put runners at first and third. Jacoby Ellsbury, who singled in his first two at-bats, popped to third. Aaron Hicks got the run home on a groundout, making it 1-1.

The Blue Jays retook the lead in the fifth. Smoak drew Pineda’s third walk — he didn’t walk more than two in any of his starts last season — and Goins doubled. With the infield back, Kevin Pillar pounded one to short. After a clean pick, Torreyes made a low throw that Teixeira couldn’t scoop, and Torreyes’ error brought in Smoak. Josh Donaldson hit another sharp grounder that Torreyes turned into a 6-4-3 double play, and Goins scored to make it 3-1.

“You want every throw to be perfect,” Torreyes said through his translator, “but sometimes it doesn’t happen.”

In Happ’s last inning, the sixth, Beltran singled with one out and Headley drew a two-out walk, but Torreyes struck out.

“He made the pitches when he had to,’’ Joe Girardi said of Happ. “I thought we hit some balls pretty hard in some key situations but they were at people. We had some opportunities to get the lead but we weren’t able to do it.”