Back in the before times, Sept. 1 was a time for well-known veterans players to receive promotions or activations en masse to contending teams looking to fill out the bottom of their roster for the playoffs.

In 2015, the last time the Mets made the World Series, they recalled or activated from the injured list a spate of journeymen types — including Eric Campbell, Kirk Nieuwenhuis, Bobby Parnell and Eric Young Jr. — on Sept. 1. Two years later, the Yankees, on their way to Game 7 of the AL Championship Series, recalled or activated Matt Holliday and Erik Kratz.

Come tomorrow, though, the Mets and Yankees will make roster moves with their eyes focused solely on a future they both hope is immeasurably better than a bleak present.

A stretch drive unlike any other in New York will begin with a trio of hotly hyped prospects — the Mets’ Ronny Mauricio and the Yankees’ Jasson Dominguez and Austin Wells — being recalled to make their major league debuts against the Mariners and Astros, respectively.

(A quick reminder that neither the Mets nor Yankees would ever be playing the Mariners or Astros in September in the before times)

The promotions should provide a pair of last-place teams a much-needed spark and reason to convince fans to keep paying attention as football takes over the calendar. But even these late-season cameos carry a degree of risk that could impact how each team acts this winter and how it is perceived.

The Mets have been under .500 and in search of a spark since early June, but Mauricio has remained at Triple-A despite a need at second base, third base and left field — positions Mauricio played at Triple-A Syracuse — and Mauricio’s success for the upstate affiliate, for whom he has put together another 20/20 season while improving his walk rate and cutting down on his strikeouts.

The New York Post reported earlier this month that the Mets were displeased with what they perceived as disinterest on the part of Mauricio. But the same things were being whispered about Matt Harvey a decade ago, and all he did upon his promotion was author 12 of the most sensational months New York has seen since Dwight Gooden’s peak.

If Mauricio has a big month, the Mets are going to face criticism for not recalling him at a point when the season might still have been salvaged. That, of course, beats the alternative, which is Mauricio struggling and the Mets wondering if another long-awaited prospect is headed for an extended learning curve or worse at the big league level. While Francisco Alvarez looks like the real deal on both offense and defense, Brett Baty and Mark Vientos are batting a combined .205 in 483 at-bats while generating -2.3 in WAR per Baseball-Reference.

Growing pains are to be expected for Dominguez and Wells, who arrive in Houston with a combined 183 plate appearances at Triple-A. The 20-year-old Dominguez is going to be the youngest Yankees player since Jose Rijo in 1984, while Wells, a 24-year-old catcher, will be subjected to the highs and lows that come with trying to hit and handle a big league staff that features a likely Cy Young Award winner in Gerrit Cole.

But considering how the Yankees’ farm system has dried up since the “Baby Bombers” emerged in 2017 — only five homegrown players not named Aaron Judge have posted a WAR of 3.0 or greater since then, and the Yankees subsequently traded Gary Sanchez and Jordan Montgomery — the beleaguered Brian Cashman needs Dominguez and Wells to appear something other than overmatched.