DETROIT — Max Scherzer’s session throwing batting practice to the Tigers punctuated a disastrous day for the Mets.

The questions can perhaps begin on whether Scherzer, the Mets co-ace, will be the same again now that he’s been busted by the rosin police.

Or was Wednesday night just a case of a rusty pitcher who had barely received work over the last three weeks?

In his return from a 10-game suspension, Scherzer failed to complete even four innings and got battered for six runs by an anemic lineup (which entered the day last in MLB in scoring) in the Mets’ 8-1 loss to the Tigers in the nightcap of a doubleheader at Comerica Park.

The Mets lost the first game 6-5 after Adam Ottavino flushed an eighth-inning lead.

It’s hardly the start the Mets needed to this 13-game stretch against underwhelming teams.

But lately the Mets, with eight losses in 10 games, have fallen into that same category.

Scherzer had last pitched on April 19 at Dodger Stadium, where he was ejected for violating MLB’s rules on foreign substances.

His ensuing suspension served, he returned to the scene of some of his great moments — the right-hander rose to prominence during his five seasons with the Tigers — and got jumped almost from the start.

Scherzer’s spin rates were down significantly, especially with his curveball and cutter.

According to Statcast, his four-seam fastball was down 107 revolutions per minute compared to his average this season.

His curveball was down 218 rpms and his cutter 222 rpms.

Spin rates generally improve with the use of substances, including rosin.

Scherzer maintained when he was suspended he had used only rosin and sweat in aiding his grip of the baseball.

But MLB is enforcing rules that were updated in spring training that consider even the excess use of rosin as a violation.

Eric Haase and Matt Vierling both homered against Scherzer, who allowed six earned runs on eight hits and one walk over 3 ¹/₃ innings.

Haase, who hadn’t homered all season before Wednesday, crushed the Mets by delivering the go-ahead hit in Game 1 off Ottavino after hitting a three-run blast against Joey Lucchesi.

The Mets will try to avoid what would be an embarrassing sweep when Justin Verlander takes the ball for his debut with the team on Thursday.

Ottavino was entrusted with an eighth-inning lead in Game 1 and got burned by a confluence of bad luck and one hittable pitch.

“I didn’t execute in the big moment there,” Ottavino said. “I have got to be better. I will be better.”

Jimmy Yacabonis pitched three perfect innings in relief, getting the ball to Ottavino with the Mets ahead 5-4.

But Ottavino allowed a bloop single to Vierling and drilled Javier Baez with a pitch before missing with a fastball with runners on second and third that Haase smashed for the go-ahead hit.

Ottavino’s blown save was the third by the Mets’ bullpen in 12 chances this season.

Ottavino, who had been perfect in his previous three save opportunities this season, was pitching for the first time since last Wednesday — he was placed on the paternity list after that game.

In three of his last four appearances he’s been scored upon.

Vierling’s single that started the winning rally landed just in front of sliding Starling Marte, who was playing deep in right field.

“I got a good jump on it — I thought I was running hard there,” Marte said through an interpreter. “But the ball was just too far and I couldn’t get there.”

Added Buck Showalter: “If [Marte] can’t catch it nobody will.”

Lucchesi lasted only four innings and allowed four earned runs on five hits with one strikeout.

The performance was the left-hander’s worst in three starts since his recall from Triple-A Syracuse.

Showalter indicated he removed Lucchesi after only 46 pitches to keep open the possibility he can be used Sunday, when the Mets are without a scheduled starting pitcher.

Haase’s three-run homer in the first started the day in the wrong direction for Lucchesi, who allowed three hits in the inning.

Baez homered leading off the third for the Tigers’ fourth run against Lucchesi.

“I feel like I calmed myself down,” Lucchesi said. “I made some bad pitches in the first, I mixed it up a little bit more [after that]. … That one bad pitch to Haase is what changed my whole outing.”