From Super comeback to embarrassing collapse.

What a strange turnaround for the New England Patriots.

The mood was so festive at Gillette Stadium on Thursday night before the opening game of the season. Fans frolicked as they watched highlights of the Patriots’ Super Bowl rally to beat Atlanta. They rocked the house when the players came onto the field and the fifth championship banner was unveiled. They even talked about a 19-0 season.

A few hours later, the Patriots were 0-1.

Yes, they could wind up going 15-1. And it’s surely not a time to panic, particularly in the weak AFC East where it’s possible combining the best players from the Dolphins, Bills and Jets still wouldn’t present a roster capable of challenging the Patriots.

But a bunch of issues cropped up as Kansas City took apart New England in the second half for a 42-27 defeat that was among the worst the Patriots have experienced under Bill Belichick.

Just listen to what Tom Brady said after the offense was ineffective and the defense got torched, particularly on long plays.

“I just think we need to have more urgency and go out there and perform a lot better,” said the now-40-year-old quarterback and four-time Super Bowl MVP who looked anything but for much of the night. “That is a winning attitude and a championship attitude that you need to bring every day. We had it handed to us on our own field.

“It’s a terrible feeling, and the only people that can do something about it are in that locker room. We’ve got to dig a lot deeper than we did tonight because we didn’t dig very deep tonight.”

That was shocking to hear. Mistakes rooted in bad decision making or inexperience, or even in a lack of enough talent are more acceptable than not having the proper mental approach. Of the criticisms sometimes leveled at the Patriots, being ill-prepared or lacking an edge rarely if ever has been one of them.

That might be the most dangerous aspect of the loss for New England.

Not surprisingly, Belichick offered far less insight into the loss than did Brady. He did, however, emphasize that only the here and now matters.

“I think I said it a thousand times. I think we’ve got a lot of work to do,” Belichick said Friday. “I don’t think anything that we did really was good enough. I’m not really interested in living in the past, in 2014, 2015, 2003, 2004, which constantly keeps coming up. I mean, everything’s about some other year, but (it’s) this year and this team. I don’t really think all that’s relevant because we’re talking about another team, but we’ve got a thousand questions about it every week.

“So, I’m really concerned about the 2017 team, what this team is, what this team needs to do. I’m not trying to live in the past like everybody else is.”

OK, so looking to the future – meaning the next few games of this schedule: at New Orleans, home for Houston and Carolina, at Tampa Bay – here are some challenges facing the Patriots that all of those predictors of perfection might have overlooked.

TEAM SPEED – The Patriots have their share of roadrunners, but overall they aren’t a fast team. That problem surfaced in pass coverage as Alex Smith torched the secondary, and when Brady was throwing. And while the Chiefs have plenty of speed demons, there are other upcoming opponents who are faster.

NO BLOUNT WEAPON – Yes, Mike Gillislee scored on three short runs, the team’s only touchdowns against KC. But the Patriots also failed on four short-yardage situations, and it’s hard to project any of the current running backs coming close to the overall effectiveness LeGarrette Blount had on the ground before leaving for Philadelphia as a free agent this year.

PASS RUSH – DE Trey Flowers is a stud, but beyond him, New England really has to search to find someone who can make QBs nervous when they want to throw. That means defensive coordinator Matt Patricia must find ways to scheme around that deficiency.

Of course, there’s no DC in the league better at putting together confounding game plans than Patricia.

BRADY’S TARGETS – For now, after Brady lost his security blanket in Julian Edelman (season-ending knee injury), he isn’t as familiar with some of his wideouts as he would like to be. That figures to develop with Brandin Cooks, Dwayne Allen and maybe Phillip Dorsett, but those short routes that Edelman and Danny Amendola (now concussed) excel at weren’t available much vs. the Chiefs.

Also, Rob Gronkowski was hardly in peak form Thursday night.

Despite those issues, the idea that the Patriots no longer are the team to beat is absurd. Unless, of course, they keep performing the same way for much of the season, which is very unlikely with Brady on hand.

But there’s also no question that, at least in early September, they have lost that air of invincibility that many observers pinned on them.

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