Francisco Lindor will almost assuredly miss one of the biggest series of the season.

But the Mets hope their shortstop will be back for their biggest series of the season.

Lindor was out of the lineup for a sixth straight game with an ailing back on Saturday, a 6-3 win over Philadelphia.

The Mets will finish this series against the Phillies at Citi Field on Sunday before an off day Monday leading into a three-game showdown in Atlanta on Tuesday.

Tuesday is the day to circle — or at least seemingly the earliest day possible — for Lindor to find his way back to shortstop.

“That’s the most likely scenario here,” manager Carlos Mendoza said of the start of a series against the Braves, which might decide which club advances into the playoffs.

Lindor feels “better,” Mendoza added, before the team’s MVP went through a workout Saturday.

Lindor played catch, took batting practice from both the right and left sides — a day prior, he only hit as a righty — and went through half-effort sprints in the outfield.

Mendoza mentioned that Lindor might take ground balls, although he did not on the field at least.

Lindor left the field smiling.

Eight days after Lindor aggravated the injury running the bases, Mendoza continued to refer to him as day-to-day.

The team’s rock had played in each of the first 147 games of the season and had been nursing back discomfort that escalated in Philadelphia on Sept. 13.

Lindor returned to the order Sunday but looked clearly hobbled and was removed after just 1 ½ innings.

On Monday, an MRI exam on his back was described as “clean” and it was estimated he would miss 2-5 days, a projection that has proven light.

Because he wasn’t progressing quickly enough, Lindor received a facet injection in his lower back on Thursday.

“Trying to do whatever it takes to come back as soon as I can,” Lindor said Friday. “It was always trending in the right direction, but it didn’t feel like I could get back sooner rather than later. And with the injection, they said there was a possibility that that could happen.”

Without Lindor, Luisangel Acuna made his fifth straight start at shortstop and has looked ready for the stage — entering play 8-for-23 (.348) in his first taste of the majors while playing solid defensively — and going 2-for-3 with a homer.

Starling Marte served as designated hitter Saturday, a spot that has normally been reserved for a struggling J.D. Martinez.

Mendoza said Lindor is not a candidate to receive time at DH, which would save him from a grueling defensive position but come with its own complications.

“He [would have to] hit and then sit down, and somehow he’s going to have to stay hot,” Mendoza said. “We haven’t gotten to that point. But the way we see it is, when he’s ready to go, he’s playing shortstop for us.”

With Saturday’s win, the Mets remained two games ahead of the Braves for the final NL wild card.

The winner of next week’s showdown also will hold the tiebreaker between the NL East rivals, a potential rubber game essentially counting as two games.

It would make sense for the Mets not to rush Lindor back before the series in Atlanta begins.

In the meantime, Lindor has been active in the dugout during games, frequently seen chatting with both hitters and pitchers.

“He’s on the infielders if they’re not moving,” said Mendoza, who is not accustomed to having his star around him so often. “But I don’t want to see him in the dugout. I want to see him at shortstop.”