ARLINGTON, Texas — You want to blame Eli Manning for Cowboys 35, Giants 17 in Sunday’s season opener at AT&T Stadium?

Go ahead. Have at it. But this loss was not on the quarterback. This loss was on exactly what we thought the Giants’ most glaring weaknesses were all along entering the season: their young, inexperienced cornerbacks and their nonexistent pass rush.

The Giants’ secondary couldn’t cover anybody the Cowboys sent out to catch passes, and their pass rush treated Dallas quarterback Dak Prescott (25 of 32, 404 yards, four touchdowns and a perfect 158.3 passer rating) with more respect than team owner Jerry Jones has in not signing him to a contract extension.

Cowboys receivers ran free like golden retrievers in a park, and Prescott had enough time in the pocket to cook dinner for his offensive linemen before throwing to his open receivers. It all proved to be a debilitating combo platter for the Giants and one they will not survive as this season progresses.

In short, the NFL debut for Giants rookie cornerback DeAndre Baker was a nightmare, and the day wasn’t much better for backup Antonio Hamilton, either. Not that this was all on those two players.

“Reality check?’’ safety Michael Thomas said. “We’ve got to get back to work. We can’t make the mistakes we made out there regardless of [whether we’re] young or not. And it wasn’t just young guys, myself included. We’ve got to get better.’’

Safety Antoine Bethea, a veteran of 14 seasons, said, “Yeah, we’re young, but we get paid to do a job, and we’ve got to do it with no excuses.’’

Bethea’s message to the youngsters?

“They’re going to keep coming at you until you start making plays,’’ he said.

Baker, the first-round draft pick from Georgia, had the roughest game of all.

“Rookie corner in the NFL, out there playing for the first time, there’s a lot to be learned,’’ Giants coach Pat Shurmur said.

With the Baker and Hamilton out there looking like raw meat to a lion (with the lion being Prescott), the Cowboys quarterback never bothered to look in the direction of Giants veteran cornerback Janoris Jenkins once all afternoon.

“I expected that,’’ Jenkins said.

Jenkins’ message to Baker and Hamilton?

“You got a lot of talent, a lot of potential, and we’ve got 15 more games to go,’’ he said. “It’s pretty tough, but you’re either going to man up or lay down.’’

The nightmare for the secondary began early, on the Cowboys’ second offensive series after the Giants had taken a 7-0 lead on the opening possession. Baker was beaten by Cowboys receiver Michael Gallup (7 catches for 158 yards) on a 13-yard completion on third-and-4 to keep the drive alive.

Several plays later, the Cowboys tied the game at 7-7 on a busted coverage that left tight end Blake Jarwin wide open on a 28-yard TD.

“It’s the NFL, so there’s no excuses about whoever they’re throwing the ball at — whether they’re throwing at me 10 times, DeAndre 10 times — we’ve got to make our plays,’’ Hamilton said. “There ain’t no excuse.’’

Baker was torched by Amari Cooper (6-106, TD) on a 21-yard Prescott TD pass that made it 21-7 Cowboys.

“I didn’t have the best game that I wanted to have, but it’s about bouncing back and showing what I can do next week,’’ Baker said. “I have to fight to through adversity.’’

A 25-yard Prescott pass to Randall Cobb (4-69, TD) made it 28-10. As if it all wasn’t enough, the Cowboys weren’t finished. They kept their final scoring drive alive with a 62-yard Prescott pass to Gallup on third-and-8 with Baker in familiar pose: trailing the play.

“He’s a big boy,’’ Hamilton said of Baker. “Nobody’s needs to hold his hand. He knows what he did wrong, so he’s going to get it right and we’re going to back him and make sure he gets it all right … as well as myself. I’ve got things I need to correct.’’

How does Jenkins, the veteran of the cornerback group, think the youngsters will come back from this next Sunday against the Bills in the home opener?

“We’re going to respond like big dogs,’’ Jenkins promised. “We came out a little short this week. We’re not far away. Just mental mistakes, small things that can be fixed in practice.’’

That all sounds good. It’s just that none of what happened to the Giants on Sunday seemed small.