Jacob deGrom is starting Thursday. Mets higher-ups hadn’t decided whether to give him seven days or eight days between starts, and ultimately settled on seven.

Mets people say they wanted to get recovering Taijuan Walker back out there in a timely fashion, too. Either way, they are wise to play it safe with the Queens jewel — deGrom’s amazing right arm. Ultimately, the Mets’ best chance to play deep into October depends on deGrom more than any other single issue.

The chance for both the Mets and Yankees to make it a real Subway Series (the October kind) is perhaps the best since 2000, when the Yankees prevailed over the Mets.

Here are four keys to getting our local teams to meet in their second legit Subway Series:

DeGrom is fine, 100 percent, A-OK, everyone around the team insists. And he’s certainly looked that way on the mound (0.51 WHIP so far). But it’s probably for the best to treat him as he is — perhaps the most talented pitcher since Sandy Koufax but also one of the more fragile.

This balanced Mets team can win a lot of games without him, as they’ve shown. But they also know their October chances rise exponentially if they can pair deGrom with Max Scherzer.

DeGrom’s made three starts after 13 months off with a variety of injuries, and he’s looked as brilliant as ever (37 strikeouts, one walk). Since the return, the range has been dominant to unhittable. If he’s out there, he’s going to be good. However, he must be kept healthy.

The Yankees tried hard for Luis Castillo, but didn’t want to part with top prospects Anthony Volpe and Oswald Peraza, and it’s uncertain if that would have done it anyway, considering the Mariners gave up their Nos. 1, 3 and 5 prospects to get Castillo.

Anyway, the Yankees were happy with Montas, whose fastball-splitter combination enabled him to strike out 207 batters in 2021 for the A’s. However, he’s struggled in two of three outings so far and has a 9.00 ERA so far in pinstripes. That doesn’t look good, but it looks worse with J.P. Sears, one of four young players sent to Oakland for Montas, posting a 1.76 mark.

And Jordan Montgomery, who went to St. Louis in the swap for Harrison Bader, has barely been touched since arriving in the National League; his ERA there is 0.36. Yankees general manager Brian Cashman said on The Post podcast “The Show” that he has “no regrets” about that Montgomery-Bader deal, saying, “We’re in the space we knew we’d be.” Meaning they understood they’d be waiting for Bader to return from a foot ailment.

Bader is now targeted to return from plantar fasciitis the first week of September, which sounds a bit better than previous guesstimates. And that would be welcome relief. On “The Show,” Cashman pointed out, “We’re plus defensively everywhere except center field.” Bader, it goes without saying, is the biggest plus defensively out there, when he can play.

Giancarlo Stanton (Achilles) is expected back Thursday, and DJ LeMahieu (toe tendinitis) is back playing already. So that leaves Matt Carpenter, who stunned folks by being their second-best offensive player before suffering a foot fracture. Boone didn’t offer the most optimistic view about Carpenter’s possible return.

“I think it’s way too early to know,” Boone said.

But Boone also stressed that they retain hope. That’s good because, since Carpenter’s been out, they’ve gone from the best offense in the league to one of the worst.

The Yankees bullpen, one of the best around most of the year, is in flux, as Boone is using a “mix and match” system to close games. Twice in the last two days he’s used a pitcher with a 6 ERA — Lou Trivino followed by Jonathan Loaisiga — to close successfully, so he’s mixed and matched nicely for a couple days, anyway.

The Mets’ bullpen is anchored by the best reliever in the game, Edwin Diaz, but still comes with questions. Adam Ottavino has done a nice job setting up, and they are hopeful the recently returned Trevor May and deadline-pickup Mychal Givens can bolster the back end. Overall, the numbers are better than you’d think, though they are somewhat skewed by having a pitcher as dominant as Diaz.

“I’ve been very proud of the job they’ve done down there,” Mets manager Buck Showalter said. While they have much clearer roles than the Yankees now, they are also awaiting some returnees. The Mets may also look down to the farm where 6-foot-7, 265-pound Bryce Montes de Oca has 44 strikeouts in 28 innings.

Meantime, Zack Britton is starting a rehab assignment, and Clay Holmes and Scott Effross are also on the mend. There’s a lot of moving parts, and much uncertainty. How they can piece things together to end games may determine both teams’ fates.