The Mets need some help for their lineup, and fast.

J.D. Martinez is getting closer to being ready to provide it.

Carlos Mendoza said prior to Thursday’s doubleheader against the Tigers at Citi Field that the veteran DH is scheduled to join one of the organization’s minor league affiliates “as soon as [Friday].”

Mendoza added they still need to come to a decision about where Martinez will end up, either with Triple-A Syracuse, Double-A Binghamton or Single-A Port St. Lucie.

And then they will determine when he’s ready to get to the majors — although it doesn’t seem as if he’ll be ready by Sunday for the final game against the Reds, which is the first day he’d be eligible.

“We’re getting close,’’ Mendoza said. “We’ve got to make a decision.”

As for the following series in Atlanta, Mendoza said, “Everything is on the table. We could see him at some point in that series [and there’s a] chance we won’t see him. We’ll see how he responds once he starts playing real games in the minor leagues.”

The 36-year-old Martinez has been getting at-bats at the team’s facility in Port St. Lucie as the Mets struggled through the first week of the regular season, with a mostly dormant offense.

Mendoza added they don’t want to rush Martinez back and Martinez will have a voice in the decision.

“He’s gonna have a strong opinion,’’ Mendoza said of Martinez, who signed with the Mets on March 23. “He knows himself better than anybody else [with] his routine and how detail-oriented he is with the feel for his swing and mechanics. We will consider those things. He’s getting a lot of at-bats, feeling good. Now we’ve got to take the next step.”

The most important thing for Mendoza is for Martinez to continue getting at-bats and reps in the field and on the bases to get back into form.

“We’ll take it one day at a time,’’ Mendoza said. “We want to do what’s right for J.D. and the team and make sure he’s not rushed and make sure not to put J.D. at risk.”

But the Mets remain confident they’ll see him soon.

The reports from Port St. Lucie, Mendoza said, have been, “Good for the most part. There are days when his timing [and] mechanics are off. He’s a very meticulous guy. … He’s moving in the right direction.”

Pete Alonso’s ninth-inning homer in Game 2 gave him 500 RBIs for his career, making the first baseman the fastest in team history to reach the milestone.

He got there in 690 games, breaking David Wright’s previous record of 727 games.

Alonso called the mark “special.’’

Yohan Ramirez was active for the second game of Thursday’s doubleheader, having served his two-game suspension for throwing behind Milwaukee’s Rhys Hoskins on Saturday.

Ramirez was initially suspended for three games before he appealed the ban and it was reduced to two.

Francisco Alvarez, the hottest bat in the Mets’ shaky lineup, was not in the starting lineup for the second game, as Mendoza tries to manage his playing time.

He pinch hit for Omar Narvaez in the seventh, flied out and remained in the game.