Chiefs quarterback Alex Smith prepares to throw a touchdown pass to Tyreek Hill. (Steven Senne/AP)

So much for the New England Patriots chasing perfection. The path to a 19-0 season required a 1-0 start, and the Patriots didn’t manage even that.

On a night that was supposed to be about reaffirming the greatness of quarterback Tom Brady and the Patriots, the Kansas City Chiefs spoiled the party. Quarterback Alex Smith threw four touchdown passes in a performance that was far more Brady-like than Brady’s, and the Chiefs emerged with a 42-27 victory Thursday at Gillette Stadium in the NFL’s season-opening game.

Patriots fans had their chance, as promised, to savor last season’s Super Bowl title and vent their hostility toward visiting NFL Commissioner Roger Goodell. But their team failed to take a first step toward potential further glory.

“It was just a very poor effort,” Brady said. “I think we’re going to have to do a lot better. . . . We just have to be a lot better in a lot of areas, starting with our attitude and our competitiveness.”

New England quarterback Tom Brady looks on from the sideline as the defending Super Bowl champions lose their season opener. (Michael Dwyer/AP)

Smith connected on 28 of 35 passes for 368 yards. Smith’s 75-yard strike to speedy wide receiver Tyreek Hill in the third quarter gave the Chiefs a 21-17 lead. His 78-yard connection with rookie running back Kareem Hunt in the fourth quarter put Kansas City in front, 28-27. Hunt added a four-yard touchdown run with a little more than five minutes to play. He finished with 148 rushing yards and 98 receiving yards and totaled three touchdowns.

That was enough for the Chiefs to win despite three rushing touchdowns, totaling five yards, by Patriots running back Mike Gillislee. Brady’s outing was ordinary, by his lofty standards, and the New England defense was extremely shaky.

“We have to get a lot better if we want to win any football games this year,” Patriots safety Devin McCourty said.

It was the most points ever surrendered by a Bill Belichick-coached Patriots team.

“We all have a lot of work to do,” Belichick said.

The victory came with a cost for the Chiefs. Safety Eric Berry was taken from the field on a cart late in the game with what was reported to be an Achilles’ tendon injury.

It is an NFL season that begins with so much focus on the unemployment of Colin Kaepernick and the legal tussle over Ezekiel Elliott’s suspension. The Patriots’ bid to maintain their supremacy over the rest of the sport is the leading on-field story line. Their uneven performance Thursday provided no firm answers as to how it might turn out. But clearly, there is much tinkering that must be done.

This is a Patriots team that ultimately might be better than last season’s version, with the offseason arrivals of wide receiver Brandin Cooks and cornerback Stephon Gilmore. Brady is on the wrong side of age 40 but shows few signs of slowing down. The loss of wideout Julian Edelman to a season-ending knee injury suffered during the preseason, though, might have provided a glimmer of hope to the rest of the league. The vulnerability of the New England defense Thursday intensified that glimmer.

It all felt quite a bit like the Patriots’ 41-14 defeat at Kansas City in a Monday night game in September 2014. That game dropped the Patriots’ record to 2-2 and produced questioning of Brady’s lasting power as an elite quarterback. It was two Patriots’ Super Bowl wins ago.

“Every position that we have is going to have to do a better job than we did tonight,” Brady said. “There was nothing really positive about anything that was done. . . . We had it handed to us on our own field. It’s a terrible feeling. 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.”

Goodell watched the game from a suite high above the field. He did not sit in the box of Patriots owner Robert Kraft. Goodell was booed by fans when he made an approximately 13-minute appearance on the field beginning about an hour before kickoff. He stood near a corner of an end zone and spoke to Chiefs owner Clark Hunt.

The entire Deflategate saga actually turned out pretty well for the Patriots. Last season began with Brady serving his four-game suspension but ended with him essentially halting all debate about which quarterback is the greatest in NFL history. The Patriots added another Super Bowl triumph to their collection. Backup Jimmy Garoppolo boosted his worth during Brady’s absence.

None of that put Patriots fans in a forgiving mood, however, toward Goodell, who’d made an appearance in Foxborough during the preseason but otherwise had not been on hand for a game here since the Deflategate proceedings. Many fans wore shirts or carried towels Thursday depicting Goodell with a red clown nose.

The pregame ceremony celebrating last season’s Super Bowl title was far from understated. There were five immense, inflatable replicas of the Lombardi Trophy placed on the field. The video board showed highlights of the Super Bowl comeback from a 28-3, third-quarter deficit against the Atlanta Falcons seven months ago in Houston. The crowd rejoiced all over again. But the euphoria didn’t last.