Home is where the offense isn’t.

There is a good reason Citi Field has become Citi Morgue, where the Mets’ offense is DOA.

Yes, there are so many places where the Mets must improve, but it has to start with the Mets’ bats on Tuesday at home against the dreadful Orioles.

The Mets enter play 15th in the NL in home OPS with a .653 mark. If that is not bad enough, they have the 29th-ranked OPS in all of baseball. Only the A’s are worse with a .645 mark.

The woes are aplenty for Mickey Callaway’s club, which has lost six straight at home. The Mets are 14th in the NL in slugging with a .350 mark, only the Marlins are lower at .349. That .350 is 29th in the majors.

At home the Mets are 14th in on-base percentage at .302 with the Dodgers last at .296. As for old-fashioned batting average, it doesn’t get any better. The Mets are 14th in the NL with a .223 average at Citi Field with only the Diamondbacks worse, batting .221 at Chase Field.

One more number to chew on, the Mets have scored only 97 runs in 29 home games this season. Derek Jeter’s tanking Marlins are the only NL team with fewer runs at 93. Only the Rays (94 in 24 games) and Marlins are in worse offensive shape than the Mets.

Just to give Yankees fans another reason to gloat, consider they lead all of baseball with 181 runs scored at home in the bandbox known as Yankee Stadium over 31 games.

A change in the Mets’ approach is necessary. A lot of this is because of injuries and Yoenis Cespedes spending so much time on the DL the past two seasons, but that’s life for the Mets. Cespedes will hit in a simulated game Tuesday well before Jason Vargas takes the mound against Alex Cobb.

Todd Frazier will return to the lineup for the first time since May 7. Frazier averaged 155 games a season over the past four seasons, but he is a Met now: Things happen.

Sandy Alderson’s offensive philosophy of walks and home runs being the basis for production could hit the refresh button. The Mets could use more first-pitch swinging and try to use much more of the field in the hopes of getting different results.

Put the ball in play.

Add Jay Bruce’s collapse into the mix and it’s a team that has little power and little ability to get on base. Not a good combination. When teams go into dramatic shifts against Bruce, it would be wise if he tried to find a way to get on base.

The Mets also suffer from an extreme lack of depth. Consider the bench players Callaway had at his disposal Sunday in the 2-0 loss to the Cubs. Now consider the bench players Joe Maddon had at his disposal. The Cubs’ depth is much better, so Maddon could rest some of his regulars until later in the game when they were needed and start with backups like Tommy La Stella.

On his bench to start the game, Callaway had Jose Reyes and his .141 average, regular second baseman Asdrubal Cabrera (.292/.335/.507) essentially Callaway’s only bullet, Jose Lobaton (.152) and Devin Mesoraco (.218).

Maddon was able to turn to Anthony Rizzo, Ben Zobrist, Kris Bryant and Chris Gimenez. Game over.

Bunting against Jon Lester was something the Mets could have done but did not do. The only Met who is not struggling offensively is Brandon Nimmo. Michael Conforto is being beat by the fastball, Bruce is popping up most everything and has only three home runs on the season. Putting a little more speed at the top of the lineup with Amed Rosario could shake things up a bit.

Callaway has to try something to get the Mets offense going, especially at home.

Sunday’s first inning set the stage for the day’s defensive disaster. After getting two walks to start the bottom of the first, the Mets could not put the ball in play, getting three straight strikeouts from Bruce, Kevin Plawecki and Conforto.

More contact would lead to more runs.