NEW ORLEANS -- It wasn't supposed to look like this. Not again. Not with a young defense that had finally turned things around so impressively last season.

But somehow the New Orleans Saints kicked off the 2018 season with a defensive flop as dreadful as anything they posted in some of those historically bad seasons between 2012 and 2016.

They allowed Ryan Fitzpatrick to throw for 417 yards and four touchdowns and run for a fifth Sunday in a 48-40 loss to the Tampa Bay Buccaneers in the Mercedes-Benz Superdome. The Bucs had more TD passes of 50-plus yards (two) than punts (one).

It was one of the biggest Week 1 surprises in the NFL -- a stunning performance from a team that was anointed as one of this season's popular Super Bowl picks.

And it's yet another slow start for the Saints, who haven't won a season opener since 2013.

"We needed this, we needed to get slapped in our face one good time to see that we're not on the level we think we're on. But we're gonna get better," Saints cornerback Marshon Lattimore insisted.

The second-year cornerback -- the NFL's 2017 Defensive Rookie of the Year -- allowed Buccaneers receiver Mike Evans to have a big day (seven catches for 147 yards and a 50-yard TD) after Lattimore had stifled Evans in both meetings last season.

It was that kind of day for the Saints' defense.

The unit also had a breakdown in zone coverage on Tampa's fourth play of the game that allowed DeSean Jackson to spring wide open for a 58-yard touchdown catch. If you're keeping score at home, that's now two 50-yard plays against a Saints defense that gave up only one play of 50-plus all season in 2017.

Fellow defensive backs such as Ken Crawley, Marcus Williams, Patrick Robinson and Vonn Bell were also victimized in what is expected to be the most talented unit on New Orleans' defense.

But it wasn't just the back end that failed to do its job. Coach Sean Payton lamented that Fitzpatrick was "pressure-free" for the most part Sunday.

"Take your pick," Payton said when he was asked what didn't work on defense. "We didn't hurry the passer. Guys were open. Third downs were awful. They had [529] yards. We didn't disrupt the timing of any element of the passing game. And too many penalties.

"I can't think of any positives."

When a reporter started asking Payton a question by saying, "Obviously anything can happen in this league at any time ..." Payton cut him off.

"That's true. And you just saw it happen. So there's no 'buts' after it. You have to come ready to play in this league, period," Payton said -- though he repeatedly credited Tampa Bay and Fitzpatrick, in particular, for doing just that Sunday.

The defensive struggles wasted a dynamic performance by the offense -- Drew Brees threw for 439 yards and three TDs, Alvin Kamara scored three times and Michael Thomas caught a franchise-record 16 passes for 180 yards and a TD. The offense also made two costly errors, though, with lost fumbles by Thomas and Mike Gillislee.

No one specifically suggested the Saints came out flat or lackadaisical or overconfident for their season opener: "I don't think anybody went out there with the mindset that [the Buccaneers] were just gonna roll over because we won the division last year," Saints defensive tackle Sheldon Rankins said. "They beat us at the end of the year last year, so I'm sure they had all the confidence in the world they could beat us. And they did."

But the result was exactly the type of "hangover" performance the Saints tried to guard against all summer.

Payton tackled those Super Bowl expectations head-on in the first team meeting of training camp, using the message "Prove Them Right" as a way to capture the same mentality of teams who are determined to prove critics wrong. The Saints had a poster with that message hanging outside their team facility throughout training camp.

And they talked all week about avoiding the slow starts that led them to records of 0-2, 0-3, 0-3 and 0-2 over the past four seasons.

But as Lattimore acknowledged, no amount of talk can do the job that they needed to actually do on the field Sunday.

"I mean, we like to do what we say, of course. But it's not always gonna end up like that. It takes time to be a great team," he said. "You know, there's a lot of new guys on the team, and we're still trying to jell together and get right.

"It's the first game. Don't panic. We went 0-2 last year and went on an eight-game winning streak. ... We're still together. We're gonna get it right."

The good news about that trend of slow starts is that the Saints have been here before. All too many times. Last season, their defense got torched for a total of 1,025 yards in the first two games of the season against the Minnesota Vikings and New England Patriots, respectively, before that epic turnaround that led to an 11-5 season and the NFC South title.

"It's not a death sentence," Rankins said. "You take it on the chin, you learn from it and you play better next week."

"Hopefully the Super Bowl isn't won Week 1," Saints defensive end Cameron Jordan said. "We've got a lot of things we have to address, and I'm my toughest critic. And I guess my dad would be my second-toughest critic -- so I'm looking forward to that phone call.

"[But] we have a 24-hour rule. We have to wipe our mind clean of this catastrophe that just happened. You can't be proud of 41 points on the board (by the Bucs offense). But we have to push forward."