ATLANTA — Kenny Vaccaro didn’t have to think hard about what went wrong Sunday afternoon.

It was right there, at the top of his mind, haunting his thoughts while he changed out of his gear in the visitors locker room at the Georgia Dome.

“It’s tackling, man,” the safety said following the Saints’ season-opening 37-34 overtime loss to the Atlanta Falcons. “I missed more in this game than I did all of last year. You have to get that corrected in practice.”

That’s where the Saints are after Week 1: looking to make corrections in practice. It’s not the way this team wanted to start.

There was talk all offseason — inside and outside the organization — about how much talent has been assembled on this roster. The goal was to begin their march toward the playoffs with the first result ending up in the win column.

Instead, the Saints made a plethora of correctable mistakes, missed a bunch of tackles, gave up 568 yards on defense (the second-most in team history) and ultimately let a game they should have won get away. But perhaps the silver lining is that New Orleans did many things wrong and still had a chance to win.

“It’s tough when you get a loss like that,” coach Sean Payton said. “There are a lot of plays you look at. You want to do a better job defending; you want do a better job on offense getting into the red zone.”

New Orleans did many of those things early in the game and went into halftime with a 20-10 lead after surrendering a last-play field goal. But the wheels began to come off in the second half, and Atlanta took advantage of the Saints’ many mistakes.

And as the momentum shifted, things continued to fall apart on both sides of the ball for the Saints. But in particular, the defense, which hoped to be one of the best units in the league, did not play anything like that and failed to check off its many goals for Sunday.

The Saints wanted to make Falcons quarterback Matt Ryan uncomfortable. Instead, he often was given a clean pocket or was impervious to pressure as he completed 31 of 43 passes for 448 yards with three touchdowns.

They wanted to bracket receivers Julio Jones and Roddy White. The duo instead combined for 12 catches for 188 yards and a touchdown.

Further down the list, basic things that are often taken for granted, such as tackling, began to fall apart.

It was a rough day, but the defense is not discouraged and feels it can use the loss as a learning experience.

“It definitely hurt,” cornerback Keenan Lewis said. “We came, we played, we didn’t get the ‘W’ — it always hurts when you don’t get the ‘W,’ especially when you take pride in what you do. That’s it. Get to the drawing board and we’ll get it fixed.”

Throughout the first half, Lewis and fellow cornerback Patrick Robinson did a good job containing Jones and White. Of the four catches, the duo made in the opening half, only one — a 2-yard touchdown grab by White — appeared to come with Lewis or Robinson in coverage.

The key to success early was that each man took a side and safety help was consistently afforded to whoever was lined up across from Jones, which essentially created a bracket around the receiver. But Jones (seven catches, 116 yards) began to break loose in the second half.

His first big play came deep in Saints territory on the first drive of the third quarter. The Falcons lined three men on the left side of the field, which forced safety Kenny Vaccaro to move down into coverage, leaving Robinson alone on Jones. The cornerback motioned a few times, as if to alert his teammates to what was happening, then dropped back to give Jones a cushion of about 10 yards once he realized no one was coming to help him.

It wasn’t enough room. Jones beat Robinson down the seam for a 27-yard gain that moved the Falcons to the 1-yard line. Two plays later, they scored to make it 20-17 and put momentum back on Atlanta’s side.

“They made adjustments and made a great play call,” safety Jairus Byrd said. “They seemed to have the right play calls for our defense and executed it.”

The Saints were fine with that touchdown. What they weren’t OK with was how the next two came together.

Following an interception in the red zone on a pass from Drew Brees intended for Brandin Cooks, Atlanta made a few short gains on its next drive before Ryan found Antone Smith on a short pass to the left.

The play should have died after a few yards, but linebacker David Hawthrone missed a tackle. As Smith worked his way downfield, Robinson, Byrd and Vaccaro also missed opportunities to bring him down. Before everyone could pick himself up off the field, Smith was in the end zone for a 54-yard touchdown.

That wasn’t the only breakdown.

After getting the ball back following a New Orleans three-and-out, the Falcons took advantage of a busted coverage that allowed Jones to get open for a 23-yard gain. A few plays later, they were back in the red zone, where the Saints again missed a bunch of tackles on a Jacquizz Rodgers 17-yard touchdown run, including one where he spun around Vaccaro.

“It sucks, but it’s Week 1,” Vaccaro said. “I’m almost glad it happened right now so we can build off this and get better and clean all of our mistakes up.”

The Saints scored with 1:24 left in the fourth quarter, but the defense quickly surrendered a handful of plays, allowing the Falcons’ Matt Bryant to hit a 51-yard field goal to force overtime. In the extra period, Colston dropped a pass and then fumbled another to allow Bryant to hit the winner from 52.

It wasn’t the way the defense wanted to start the season. This group envisions itself as one of the best in the league and still plans to assert itself as such.

This was a hiccup that will get corrected, the players said.

“It happens sometimes. Look at the greats — it happens to them, too,” Lewis said. “We’ll get it together, though. I promise you that.”