The Mets' Jacob deGrom pitches for Triple-A Syracuse against Omaha in...

The Mets' Jacob deGrom pitches for Triple-A Syracuse against Omaha in Syracuse, N.Y., on Wednesday. Credit: The Post-Standard via AP/Scott Schild

MIAMI — Three hundred and ninety-one days later, Jacob deGrom will pitch again.

The Mets ace is scheduled to come off the injured list and pitch Tuesday against the Nationals, a source said. That will be deGrom’s first appearance in nearly 13 months.

Manager Buck Showalter declined to officially make that announcement Saturday afternoon, preferring to wait until deGrom completes his bullpen session Sunday morning. But a person familiar with the plans said deGrom physically is ready, so unless something unforeseen arises — such as an illness or an injury — he will take the mound Tuesday.

“We’ll see how the work day goes tomorrow,” Showalter said. “We’ll have something to say tomorrow about it. Sorry.”

Because he reached only 67 pitches in his most recent minor-league game, the last outing in a rehab assignment that lasted almost a month, deGrom will need to be on a lower-than-normal pitch count in his season debut — and perhaps the games after that. Even last year, when deGrom appeared to reach new pitching heights before getting hurt, he threw as many as 100 pitches only once in 15 starts.

He hasn’t pitched since July 7, 2021, because of a series of injuries. Elbow problems cost him the second half of last season, robbing him of a chance at what could have been a third Cy Young Award in four years after he had a 1.08 ERA in the first half.

He said he was healthy upon reporting to spring training but wound up being diagnosed late in camp with a stress reaction in his right shoulder blade. That cost him the first four months of this season.

That deGrom finally will get the ball about an hour after the trade deadline — 6 p.m. Tuesday — is appropriate given what Showalter said in the days after deGrom’s stress reaction was discovered.

“Think about how strong he’s going to be as the season progresses,” he said on April 2. “What’s the trade deadline nowadays? That’s a pretty good addition. Instead of a trade, Jacob deGrom.”

DeGrom going Tuesday (on extra rest) means Max Scherzer will get the ball Monday (on regular rest), giving the Mets their first regular-season look at the co-ace dynamic that was anticipated when they signed Scherzer to a record contract last offseason.

With deGrom, the Mets will be adding to what already is a strength. Taijuan Walker, Chris Bassitt and Carlos Carrasco round out a rotation that ranks sixth in the majors with a 3.64 ERA — and has been even better lately.

What impact will deGrom have on a team that has been in first place in the NL East virtually all season?

“Make a good team better,” Scherzer said. “It’s hard to say more than that, because there’s nothing more than that. He just needs to be healthy. There’s no point at going any deeper than that.”

Scherzer, who mentioned during his introductory news conference that pitching alongside deGrom was among the reasons he wanted to join the Mets, said he was tempering his excitement about that finally becoming reality because it isn’t quite reality yet — at least not for a couple of days. So far it’s still hypothetical.

“There’ll be more to it once he pitches,” he said. “You gotta pitch. It’s all talk right now. It’s more fun when what goes on out there, when we feed off [each other], everybody feeds off. We haven’t had anything yet.”

In case you forgot …

What Jacob deGrom has meant to the Mets since he won his first Cy Young Award in 2018:

Year      Games  W-L       ERA       WHIP

2018*   32          10-9      1.70       0.912

2019*   32          11-8      2.43       0.971

2020      12          4-2         2.38       0/956

2021      15          7-2         1.08       0.554

*-Won NL Cy Young Award

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