ST. PETERSBURG, Fla. — The future is now for Oswald Peraza and the Yankees.

The Yankees called up their No. 3 prospect on Thursday, with rosters expanding to 28 for the final month of the regular season. The 22-year-old was pulled in the middle of Triple-A Scranton/Wilkes-Barre’s game Thursday. Earlier in the game, he had hit his 19th homer of the season.

Taking Peraza’s spot at SWB will be top prospect Anthony Volpe, who will be promoted from Double-A Somerset, according to sources.

Peraza will arrive to a Yankees team that just finished an ugly August and be added to an infield mix that’s not producing — and with Anthony Rizzo’s back issues potentially keeping him out for at least the next three games, Aaron Boone said on ESPN Radio.

Isiah Kiner-Falefa, fresh off a costly error in Wednesday’s loss to the Angels in Anaheim, got support from Boone both after Wednesday’s game and again on ESPN radio Thursday — before the move for Peraza was made official — with the manager saying, “I would say he’s been in the top five to seven defensive shortstops [based on advanced metrics] this year, without question.”

Many would argue with Boone’s belief in Kiner-Falefa’s defense, and defensive metrics are notoriously difficult to rely on, as indicated by the fact that some metrics have Kiner-Falefa ranked 23rd in the majors in outs above average, while Fangraphs has him fourth in the majors with 11 defensive runs saved.

What can’t be debated is that there’s a higher ceiling for Peraza’s bat than there is for Kiner-Falefa’s.

The Yankees have loved Peraza’s glove for years, and he has been solid — if not spectacular — at the plate, with a .769 OPS in 427 plate appearances.

The skills are among the reasons the Yankees sat out last offseason’s free-agent shortstop market — because the organization was high on both Peraza, as well as their top overall prospect, Volpe, who is playing well at Double-A Somerset.

Since Peraza is already on the 40-man roster, the Yankees don’t have to make another move.

The next question is how Peraza will be used.

Oswaldo Cabrera has played well at four different positions after he was called up from SWB, Cabrera, 23, has played just about every game since getting to the majors.

Peraza has primarily played shortstop in the minors, but does have some experience at second base.

DJ LeMahieu hasn’t looked right since being sidelined with a toe injury.

In his past 17 games, he’s just 10-for-66 with no extra-base hits and 16 strikeouts.

Despite the slump, LeMahieu has mostly remained at the top of the order, leading off the past three games. And Gleyber Torres had just five RBIs in August.

Marwin Gonzalez will be back with the team Friday, reinstated from the paternity list to fill the other roster spot, as Tim Locastro figures to stick around as a pinch runner.

Harrison Bader told The Post’s Jon Heyman on Thursday he’s feeling better and expects to be back from plantar fasciitis by Sept. 15. He’ll provide some defensive help and allow Aaron Judge to play more right field, but he isn’t expected to help the offense much.