Carlos Mendoza’s very modern strategy not to automatically utilize his best reliever in the ninth inning makes perfect Mets sense. Calling upon his best when the Phillies have their best hitters due up late — whether that be in the seventh, eighth or ninth inning — surely is the correct way to go. We don’t need an Ivy League analytics degree to realize that. 

The only unanswerable question here is this: Does Edwin Diaz remain their best reliever? 

It’s probably folly to try to guess correctly who among Mendoza’s other imperfect options could possibly outpitch Diaz now. So expect no real talk of a Diaz demotion. Diaz has more ability, a better résumé and a bigger contract than any other option (and actually has a bigger contract than any reliever ever). 

Mendoza frequently mentions that Diaz is “my guy,” and beyond that being an attempt to bolster Diaz, who once admitted to a confidence issue, it’s very likely the truth. 

Diaz is his “guy.” But is he the guy who can get it done now? At least a couple recent outings raise that unexpected question. 

One rival scout wondered aloud if Diaz will be better in the comfort of home as the Division Series moves to Queens after a crazy, seemingly endless journey to Atlanta, then Milwaukee, then back to Atlanta, then back to Milwaukee, then Philly. 

“I do think the Citi Field adrenaline will assist,” the scout said. “Let the trumpets sound!” 

Other scouts noticed a variety of possible issues after he surrendered three runs and the lead in a heartbreaking, 7-6 Game 2 defeat, eventually won on a walk-off hit by Nick Castellanos against Trevor Megill in the ninth inning, to even the series. 

Here are a few possibilities (with thoughts from scouts): 

1. Diaz’s fastball. “Can’t throw his fastball for a strike. He’s clearly fighting himself, especially on his fastball. Too many sliders.” (Seventeen of 25 pitches were sliders.) 

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2. Diaz’s slider. “His slider was just not good at all [in Game 2,] which may indicate fatigue.” 

3. Diaz’s command. “His command is just bad. It was like that earlier in the year, too. He has to somehow figure out how to command his fastball again. Otherwise he will never get back to what he was.” 

4. Diaz’s confidence. “I just think his confidence comes and goes.” 

5. Diaz’s workload. He threw 130 pitches over eight days, The Athletic pointed out. While he did have two days off heading into Game 2, that’s a lot. 

Mendoza’s call to summon Diaz to face the top of the Phillies lineup was expected, anyway. And it’s fair to ask: What choice does he have? 

The Mets bullpen, seemingly in a constant state of flux, has several candidates for late, high-leverage spots but no obvious alternative to Diaz, who rescued the Mets and pitched them into October after insisting he remain in Game 161 after his meltdown in Atlanta. 

“I feel 100 percent confident,” Diaz said after Game 2. “It’s part of the game. We were playing a really good team.” 

Other, better options aren’t obvious, anyway. 

Follow The Post’s coverage of the Mets in the postseason:

Ryne Stanek blew away the Brewers for one inning and he throws 99 mph, but he’s given up eight homers this year. 

Phil Maton generally is solid. But he throws only 91-92 tops and got rocked one game in Milwaukee, allowing two homers. 

Jose Butto was brilliant in two scoreless innings in Brew City, then gave up back-to-back home runs there a couple days later. 

Maton and Stanek were nice July pickups, but with the Mets merely on the cusp of the race, team higher-ups understandably didn’t want to trade big prospects for back-end bullpen pieces. Two other teams in this National League derby with less need did acquire established closers. 

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These very Phillies got Carlos Estevez, who pitched a clean eighth inning in Game 2. The Padres hit the jackpot, acquiring a trio of excellent relievers — Bryan Hoeing, Jason Adam and proven closer Tanner Scott. 

The Mets didn’t seem very involved with any of them, no surprise since they trailed in the standings and the asks were steep. 

Attrition cost them, too. Brooks Raley, Drew Smith and Sean Reid-Foley all went down with injuries. Jorge Lopez was dispatched after a bad quote. (We still aren’t sure whether he meant the Mets are the “worst” team, but if he did, he wasn’t close to correct.) 

So Diaz understandably remains Mendoza’s guy. Very likely, he still gives them the best chance. 

Things actually started great before going haywire in Game 2, as Diaz whiffed Phillies leadoff hitter Kyle Schwarber (0-for-9 with seven K’s vs. Diaz) to end the seventh, then Trea Turner to begin the eighth. Diaz was looking dominant. But suddenly, it all fell apart. 

He pitched carefully to annual October dynamo Bryce Harper, a little too carefully. After walking Harper and failing to retire Castellanos, who singled, Diaz tried a 3-2 slider on Bryson Stott. As Mendoza noted, “It didn’t do too much.” 

Stott lined a triple down the right-field line, giving the Phillies the lead and inspiring more theories about Diaz’s possible issues. They won’t stop until Diaz starts pitching like himself.