The Celtics took the court Friday night for the first time since 2010 with the chance to clinch Banner 18.

It was over by 9 p.m.

The Celtics tapped out in the first quarter.

It was Boston’s 100th game of the season.

And by far its worst.

The Celtics didn’t choke. That would require effort.

They quit.

The silver lining is that Boston has a chance to win Banner 18 at home Monday night. NBA teams up 3–0 games are 156–0 in the playoffs.

Unfortunately, these Celtics left a teeny, tiny opening for that number to become 156–1.

Boston has a 94.7% chance to win the NBA Finals ahead of Game 5, according to oddsmakers and math.

The Duck Boats are ready.

But the Fat Lady rested her vocal cords Friday.

The fat guy, however, unloaded.

Charles Barkley called Boston’s performance “embarrassing.”

“They came out nonchalant, lackadaisical,” Barkley said postgame on NBA Network. He plans to call it quits after next season. “That was so unprofessional the way they played that game tonight.”

And no one knows better than Charles what it is like to be on the precipice of a championship without being able to close the deal.

After the game, they dropped streamers in Dallas. Streamers. Red is still screaming from the Great Beyond about those balloons from Game 7 in the 1969 Finals that still hang in the rafters of the long-since demolished LA Sports Arena. That series was the first and last time a player from the losing side, the late, great, NBA logo Jerry West, was named series MVP.

If/when the Celtics wrap this thing up, it would not be unreasonable to see Luka Doncic get serious consideration for Bill Russell NBA Finals MVP Trophy honors. One can make the argument that if the sloppy Slovenian didn’t foul out in Game 3, this series might be tied.

The trophy remains Jaylen Brown’s to lose.

Thanks to a 38-point disembowelment of the Celtics Friday night, Dallas has outscored Boston in this series 408–402.

But streamers.

After cutting the series lead to 3–1?

Act like you’ve been there, guys.

That was reminiscent of the days when teams like the Jaguars would celebrate their Super Bowl championship by beating the Patriots in September.

These Mavericks show few signs of becoming the 2004 Red Sox, or the 2010 Flyers. The bigger concern would be the Celtics becoming the 2004 Yankees, or 2010 Bruins.

Luka and Kyrie shone in Dallas. But Kyrie has been spooked at TD Garden since he stepped on Lucky at midcourt. He remains more A-Rod than Big Papi.

Check back with us before Game 7. If there’s even a Game 6.

Meanwhile, the TD Garden party turned into an Irish Wake. The bash delivered the requisite brawl shared across social media that happens when your team is behind 90–62 in the third quarter. The engaged combatants still exerted more effort than the team they paid to watch on the Jumbotron.

It’s too soon to panic. This is more like the unease that comes with a hurricane forecast. Or a biopsy.

Victory Monday night and all that happened — or didn’t happen — Friday night will be forgotten before the parade begins.

There’s plenty of numeric karma lining up for Boston to win it all at home. The Celtics won Banner 17 on June 17. 6/17. Monday is June 17. 6/17. Boston is in the 617-area code.

A sizable Boston victory Monday night is more probable than not. Boston is a 7.5-point favorite. The Celtics — who had not lost since May 9 — recovered from a 135-102 loss at Milwaukee on January 11 with a 145-point performance two nights later.

To a man, the Celtics gave Dallas the deserved credit. An A+ for sportsmanship. But Joe Mazzulla failed to deliver the necessary thrashing that his team deserved for its anti-effort. When the Celtics fell behind to Miami 0–3 last season, Wyc stormed into the locker-room and tore into his players.

A little shame here wouldn’t hurt.

Not closing out Dallas in four games would be no big deal if the Tatum-Brown Celtics did not earn the reputation of failing to step on the throat of their opponents when it matters most.

Yes, the Celtics have delivered throughout this postseason. All the more reason why Friday’s flop surprised so many, including the overwhelming percentage of the money that rode with Boston to send the Mavericks fishing.

Game 5 carries the most weight of any Boston has played this season. And with that comes the most pressure. That grows exponentially each time this series continues.

If this series has a turning point, it would be in Game 3 when the Celtics led 91-70. Jayson Tatum, -33 Friday, blew a kiss to the Dallas crowd. Starting at that moment, through the first half Friday night, the Celtics were outscored 89-50 over a span of 34:18.

Tatum surpassed his idol Kobe Bryant by posting a -30 or worse in an NBA Finals game for a second time. Before Friday, both had done it once.

When the game was still winnable, Boston missed open shots, clanged layups, did not defend, and stood affixed to the court when rebounds were swiped by the Mavericks.

So much for the rubbish take that this team hasn’t been tested.

But the biggest test they face remains within.

That’s always the toughest one to pass.

Bill Speros (@BillSperos and @RealOBF on X) can be reached at bsperos1@gmail.com.