ARLINGTON, Texas — It was as bad as anyone imagined it might be.

And perhaps worse.

Everyone paying attention realized the defense the Giants put on the field this season would be challenged, based on its youth and suspect talent, often a deadly combination. Everyone knew this offense, once again directed by Eli Manning, needed a heavy dose of Saquon Barkley to keep things humming on the ground to prevent overreliance on the quarterback’s 38-year-old right arm.

Everyone knew failure to sustain this balance would lead to painful Sundays for the Giants, and they experienced the first of what may be a whole bunch of them in an opening day thud that resulted in a 35-17 loss at AT&T Stadium and triggered far more questions than answers.

The game was so one-sided that coach Pat Shurmur opted to pull Manning and allow rookie Daniel Jones to make his NFL debut late in the fourth quarter. If a Giants defense that at this point can only be described as dreadful cannot get its act in gear, the season will fall by the wayside and Shurmur will have no choice but to make the permanent move to Jones if the team never approaches contention for anything other than a high draft pick in 2020.

“We have plenty of work to do,’’ Shurmur said. “There’s some stuff we’ve got to get cleaned up and they need to improve quickly.’’

The promise of a quick 7-0 lead instantly devolved into the reality that a blowout was brewing. The Giants were not bad on defense — they were worse than bad, often downright ugly and at times looked chaotically unsure whether or not they were supposed to cover any receivers. More often than not, they did not.

Manning, making a start at quarterback for the 16th consecutive year, was what he is at this stage of his career. He went 30 of 44 for 306 yards, one touchdown and no interceptions for a rating of 95.5. He is way down the list of culprits for this mess. Jones completed three of his four passes for 17 yards but lost the fall on a fumble on his only rushing attempt.

“For the most part, especially early in the game, we moved the ball well,’’ Manning said.

The Giants lost to open a season, again, giving them a record of 0-1 for the eighth time in the last nine years. In Week 2, the home opener against the Bills, the

Giants will try to prevent starting a season at 0-2, which they have done five of the last six years.

The Giants have lost five consecutive games to the Cowboys in what the last few years is a one-sided rivalry.

The Cowboys did not even need much from star running back Ezekiel Elliott (13 carries for 53 yards and one touchdown), who missed the entire preseason in a contract holdout. Prescott might not have needed to get his uniformed cleaned, as the Giants defenders certainly did not get any fingerprints on him. Prescott finished with 405 passing yards and four touchdowns for a perfect passer rating of 158.3.

Down 28-10 in the third quarter, the Giants faced third-and-2 from the Dallas 2-yard line and then fourth-and-1 on the Dallas 1-yard line and, somehow, Saquon Barkley never touched the ball. Fullback Eli Penny was stopped for 1 yard on third down and Manning’s fourth-down rollout to his right turned into an ugly sack-fumble when he was overrun by DeMarcus Lawrence.

“We should have gained more yards on the one to Penny and then we got to do something when we roll out,’’ Shurmur said.

“As a competitor you want the ball in your hands,’’ Barkley said. “You’ve got to trust your teammates. That’s what I do. I’m not going to question the calls. I believe the calls are right.’’

Barkley ran for 120 yards — he burst open for 59 yards on his first rushing attempt of the season — but carried the ball only 11 times, as the Giants fell behind and ditched their ground game.

Three of Prescott’s touchdown tosses came with the greatest of ease, as he feasted on absolute busted coverage, leaving his targets running free. The Giants alternated cornerbacks opposite Janoris Jenkins, starting Antonio Hamilton and subbing him with first-round pick DeAndre Baker, who missed time this summer with a knee injury and apparently was not ready to handle a full workload. Prescott simply threw to whichever receiver Hamilton or Baker was trying to cover.

“You’d have to ask them if that was their strategy,’’ Shurmur said. “It seemed like that’s where the ball was going.’’

Manning realized “the game was kind of out of reach at that point’’ and thus had no problem taking a seat to give Jones his first NFL action.

“I thought it was the right thing to do to get him some work,’’ Shurmur said. “An obvious situation in my mind to put him in the game, and that’s it.’’

If the defense does not get its act together, getting Jones on the field could be a weekly occurrence.