Never did linebacker Alec Ogletree’s preseason proclamation that the Giants could be a top-10 defense in the NFL sound more like hubris than during Sunday’s season opening undressing at the hands of the Dallas Cowboys.

Cowboys quarterback Dak Prescott launched an all out assault on inexperienced Giants cornerbacks. Prescott finished with a perfect 158.3 passer rating while completing 78.1 percent of his passes for 405 yards and four touchdowns.

Running back Ezekiel Elliott, in his first time stepping onto a football field since January, averaged 4.1 yards per carry and scored a touchdown in his return from a lengthy holdout, with a new contract in hand.

Along the way, the Cowboys converted 6-of-10 third downs.

“Numbers is numbers," Giants cornerback Janoris Jenkins said Sunday. "They’re just numbers. It’s Week 1. We have 15 weeks left. We just have to get back to work.”

Despite being run out of AT&T Stadium, 35-17, Ogletree still believes in the Giants’ defense’s potential.

“No, it doesn’t,” Ogletree told reporters on a conference call Monday, when asked if Sunday changes his outlook on the season.

There’s not much else that Ogletree, a defensive captain, should be expected to say. However, it’s difficult to envision the defense that walked off the field on Sunday coming close to his preseason expectations.

"It’s a long season and this is one game, "Ogletree said. "We have the right people, we have the right scheme and everything. It’s just a matter of going out there and doing it.

“You can’t talk about it, you have to go out and do it, and we definitely are going to do that. My confidence hasn’t been shaken in our defense. I know we have a great defense here, and it’s just a matter of us doing it, and doing it on Sunday.”

Ogletree’s poor play in coverage continues to be a going concern for the Giants. He was caught biting on a play-fake on Prescott’s first touchdown pass of the game to tight end Blake Jarwin.

Overall, the Giants’ defense graded out as the worst in the league by Pro Football Focus. That’s saying something, after the Miami Dolphins surrendered 59 points in the opener to the Baltimore Ravens.

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Returning home as 2.5 point underdogs to the Buffalo Bills on Sunday, followed by a trip to Tampa Bay to take on the Buccaneers in Week 3, things could quickly snowball in the wrong direction if the defense doesn’t quickly right the ship.

Despite not being able to generate a pass-rush, get off the field on third down, or stop the Cowboys from scoring during a torrid stretch where Dallas reached the end zone on four straight possessions, confidence remains high in the defense’s side of the locker room.

“It doesn’t shake me,” Giants outside linebacker Lorenzo Carter told NJ Advance Media. “Let’s go to work. It takes a lot more than a loss to shake me.”

Matt Lombardo may be reached at MLombardo@njadvancemedia.com. Follow him on Twitter @MattLombardoNFL