If you’re a manager, look at it this way: You have a pitcher who’s top of the line enough to be the league’s defending Cy Young Award winner. You don’t have any of the catchers to whom he threw to win that award. This year, you have one catcher with whom he has a 5.33 earned run average in five starts throwing to him, and another with whom he has a 0.43 ERA in three starts.

You have the data and you’ve seen it in live action. Who do you send behind the plate to give your ace, and your team, the best possible chance to win? Should be the proverbial no-brainer, right? Especially if you were once a well respected pitching coach who should know these things.

And your number one job as a manager, other than navigating assorted clubhouse personalities and tensions, is giving your players and thus your team the best possible chance to win. So you see your ace working to a 0.43 ERA and think to yourself, that’s the catcher who ought to be working with him if you want to win. Right?

If you’re embattled Mets manager Mickey Callaway, apparently, wrong. Even if the ace in question is Jacob deGrom. Even if his ERA with Wilson Ramos behind the plate is 5.33 but his ERA with Tomas Nido behind the plate is 0.43. They’re both new to working with deGrom but Nido’s apparently doing the better job with him. This isn’t the time to double down against the idea of a personal catcher especially for a defending Cy Young Award winner.

DeGrom is too team oriented to think about it, apparently, but the manager’s job includes thinking about things his players might not ponder otherwise. But Callaway insists, and I quote, “Things aren’t going well enough for anybody to demand their own catcher.” Even though deGrom hasn’t asked for one yet.

If he’s actually aware that deGrom is doing better with Nido behind the plate, Callaway ought to reconsider while he still has his job. Which too much speculation says he won’t after this weekend. The Mets pitchers overall have a 4.37 ERA with Ramos behind the plate and a 3.20 with Nido behind the plate. Which part of that difference doesn’t register when Callaway reads the data?

It’s rare for a theoretical contending team to face a must-win series against their division’s saddest sacks, but that’s just about what the Mets faced when they opened this weekend’s set with the Marlins.

And they got swept by the Fish. It might be a little too soon to say, “Season over,” but it’s not exactly unfair to say, “Season has only two fingertips hanging onto the high wire,” either.

On Friday night, even allowing that he hasn’t got the best bullpen in the league to work with overall, Callaway inexplicably left deGrom in to take a seven-run beating in five innings that shouldn’t have gone that far. He had nobody prepared when deGrom looked early enough like he didn’t have it that night. And his catcher was Ramos.

On Saturday, Pablo Lopez and two relievers one-hit the Mets, 2-0. Steven Matz returned from a brief injured list sojourn to work three and two thirds rusty innings surrendering both Marlins runs and three Mets relievers kept the Fish shut out the rest of the way.

Come Sunday, Noah Syndergaard kept the Marlins to a pair of runs they didn’t begin to pry out of him until the sixth, but Sandy Alcantara picked the perfect day to pitch a two-hit shutout with the Mets making it only too easy for the Marlins righthander. Nido caught Syndergaard for the first time this season. Syndergaard’s previous starts saw him throwing to Ramos and posting a 4.02 ERA with him behind the dish.

Calloway had another problem on Friday night when veteran second baseman Robinson Cano jogged up the first base line on a double play grounder in the seventh. Cano admitted he thought there were two outs, partially thanks to a scoreboard error he spotted as he left the batter’s box. The manager handled it not too far removed from the indulgent mother reassuring Junior that it wasn’t his fault he put his foot through the neighbour’s china closet, the china closet had no business being there.

You don’t want Callaway to read Cano the riot act, but you didn’t necessarily expect him to hand Cano a pass, even a veteran’s pass. If anything, you’d think veterans know enough to keep their heads in the game without the scoreboard’s help. Cano was apologetic after that game but, even so, Callaway needed to take a firm enough hand. Cano didn’t face anything like a benching the rest of the weekend.

And it bit Callaway in the wrong possible spot again come Sunday. In the top of the fourth, with J.D. Davis on first, Cano whacked a dribbler in front of the plate and stood there for the most part, arguing the ball was foul (it wasn’t) while the Marlins turned a 1-6-3 inning ending double play.

None of the foregoing, of course, could put anything into the Mets’ mostly feeble bats otherwise this weekend. They scored six times Friday night and those were the only six runs they’d score on the weekend. The Marlins’ pitching took care of them effectively enough.

But why wasn’t deGrom afforded the chance to throw to the catcher with whom he and the Mets’ staff overall, while we’re at it, are getting his best results so far? Nido isn’t much of a hitter and I get that, but if you think a catcher’s number one job is handling his pitchers and calling games, you should be thinking maybe Nido gives you a better chance to help keep the other guys at bay.

At least until you find someone who can catch as well as Travis d’Arnaud did last year while being able to hit the way Ramos once did. D’Arnaud became expendable this year with Ramos’s arrival and his own futile season opening, but last year the Mets’ overall ERA with d’Arnaud behind the plate was 1.85.

And if the Mets are going to be as inconsistent as they’ve been so far at putting runs on the board, they need all the help they can get at keeping the other guys from putting runs on the board.

“If you start allowing somebody to pick their own catcher, then Ramos is not going to start four days in a row and then Nido is going to catch deGrom. That is not something that is going to be helpful to our team,” Callaway said before Sunday’s game. “It’s better to throw to whoever is catching that day and just get it done.”

Uh, no it isn’t. If Jacob deGrom’s working better with Tomas Nido behind the plate, you run Nido out there every time you give deGrom the ball until or unless Nido begins to falter on the job. You don’t have to let every pitcher on the staff pick his catcher, but you give a defending Cy Young Award winner at least some respect enough to let him pick the guy to whom he’s most comfortable throwing.

It’s not exactly unheard of. Ordinarily a team might allow a pitcher a personal catcher on behalf of giving the regular catcher a little rest, and if there’s any fielder who can use it it is the catcher. But otherwise a team might notice a pitcher doing particularly well with one catcher as opposed to others on the roster and make sure that catcher and that pitcher are hooked up regularly.

The point is to win. And if that gives you the best chance to win, go for it. Yogi Berra didn’t become a Hall of Fame catcher by hitting alone. You can look it up: in all his years as the Yankees’ number one catcher, Yankee pitchers not named Hall of Famer Whitey Ford did better with him catching than they did with any other Yankee catcher. And almost all of them pitched better as Yankees than at other times in their career thanks to having Yogi behind the plate.

Nido also can’t help the Mets with other issues. They’re last in the league in defensive runs saved; they’re fundamentally lacking; and, Callaway’s modest response to Cano’s double play misadventures simply added to any perception that he’s not the motivator, never mind tactician, the Mets need. Especially after Junior thanked Mama by putting his foot through the neighbour’s china closet for the second time in three days.

Marry that to this former pitching coach’s inability to keep a defending Cy Young Award winner in a comfort zone and put three other starters into the best conditions to work well, not to mention mal-managing a bullpen that wasn’t exactly great overall but wasn’t exactly full of rag arms, either.

It’s the formula by which a manager whose team was expected to contend this season finds himself facing a possible firing squad. And if the Mets are rounding up the firing squad, they should be pondering who’s going to succeed the fallen. Possibly as soon as Monday. When the Mets come home to open a set against the equally sputtering Nationals, who have issues aplenty of their own.

Incumbent bench coach Jim Riggleman might be a sort-of consensus interim choice despite his less-than-stellar overall record, but currently-exiled Joe Girardi and Dusty Baker may be wishing and hoping. Just don’t cast your lonely eyes upon Mike Matheny or Buck Showalter. When push comes to shove, they’re too wedded to their Books.

The Mets need to think beyond The Books if they’re going to throw the book at Callaway. And, the switch.