Eli Manning began walking out of the Giants locker room, away from a preseason he would rather forget, towards the Lions and the start of a regular season that appears clouded with major uncertainty.

Nothing that happened over the summer or again Thursday night can possibly inspire confidence that Manning and the Boys of Bummer have begun to master Ben McAdoo’s West Coast offense with so precious little time remaining on Tom Coughlin’s alarmed clock.

And yet here was Manning, following a 1-for-4 for zero yards night against Bill Belichick’s backups, following a 20-for-41 for 188 yards and one touchdown and one lost fumble preseason, refusing to believe that he will not be able to flip the switch once the real games begin in earnest and lead an offense that scares the opposing team instead of his own coaches and fans.

“I think this offense will be different, we’ll be able to move the ball, make plays, and we’ll figure it out,” Manning told The Post.

To which worried old Giants fans say: From his mouth, to Wellington Mara’s ears.

Because right now, the state of Manning’s passing offense can be summed up thusly:

Uh, oh. Or, Uh, O.

And:

Oh, no. Or, O, No.

If Manning and the Giants’ offense truly plan on heading into the regular season feeling better about themselves, they may want to consider hypnosis. Or a good shrink.

What disturbed Coughlin most after completing a 5-0 season with a 16-13 victory over the Patriots was a miscommunication between Manning and Rueben Randle.

“I thought, he thought — one of those kind of things,” Coughlin said. “Everybody in this room’s tired of hearing that stuff. There’s no place for that.”

Repeat after me, and repeat after Eli: preseason means nothing.

Except when you are installing a new offensive system that has made a two-time Super Bowl MVP quarterback look like a rookie.

“Good to get out, and get out healthy,” Manning said.

Coughlin begrudgingly stuck to his plan giving Manning and the first-team offense two series (eight plays) in an effort to have them build on the two-minute TD drive against the Jets.

“If they wanted to play more,” Coughlin said, and for some reason chuckled, “they should have made some first downs and stayed out there.”

More than anything else, it is the state of the NFC East, where you find no Seahawks, 49ers, Broncos or Patriots, that can yet be a saving grace for the Giants.

The Eagles, defending division champs, are The Team to Beat, but it isn’t as if they are some unbeatable powerhouse.

LeSean McCoy is arguably the best running back in the game and a Lethal Weapon in Chip Kelly’s offense, but:

Nick Foles won’t be repeating his 27-2 touchdown-to-interception ratio anytime soon, especially with DeSean Jackson catching passes now from Robert Griffin III.

Defensive coaches like Perry Fewell will have greater familiarity with the Kelly offense.

The Eagles owned the league’s worst pass defense in 2013.

The Giants don’t play the Eagles until Oct. 12, giving Manning and McAdoo five games to get their ship together.

And who knows? Maybe that will give Odell Beckham Jr.’s hamstring enough rest for him to join the season.

The Giants’ first division game comes Sept. 25 at FedEx Stadium, not a particularly daunting task given RGIII’s struggles in Washington rookie head coach Jay Gruden’s offense and a defense that must have Dave Butz, Charles Mann, Dexter Manley and Darrell Green cringing.

Big Blue’s upgraded secondary will likely be able to match up with Jackson, Pierre Garçon and tight end Jordan Reed.

The Giants meet the Cowboys on the road on Oct. 19. The Cowboys’ defense, without DeMarcus Ware, Jason Hatcher and Sean Lee, can serve as a cure for what ails any offense.

“We gotta keep finding a way to get into a rhythm early,” Manning said. “That’s something we haven’t been successful at, but we’ll figure it out.”

The Giants will start the regular season 0-0. And the next Super Bowl the Lions, Cardinals and Texans, their first three opponents, win will be the first Super Bowl they will have won. So there’s that. And Manning promising to figure it out. There’s your glass half full.