Jayson Tatum fell crashing to the floor hard. His one-legged, impossible fadeaway jumper at the buzzer had missed, just like so many other Celtics shots on this night. Jamal Murray tossed the ball full court as the Nuggets pulled off what no other team has been able to do this season.

For the first time, the Celtics lost at home on Friday night. It came at the hands of the defending champions, showing them that there’s still plenty to improve on over the second half of this season before their attempt to finally get over the hump this spring.

The final shot was almost fitting. Tatum scored 22 points on a rough shooting night, Jaylen Brown had just 13. The Celtics wilted offensively in the second half and in crunch time as bricks piled up. They had no answer for Nikola Jokic, who finished with 34 points, 12 rebounds and nine assists, or Murray, who had 35 points including a dominant fourth quarter as they handed the Celtics a crushing 102-100 loss at TD Garden.

The Nuggets showed their championship mettle. Their championship duo of Jokic and Murray was too brilliant as they combined to go 29-for-43 for 69 points, while Tatum and Brown combined to shoot 15-for-43 for just 35 points. The Celtics, while they liked the looks they took, scored just 39 points in the second half and couldn’t make a play when they needed to.

“They’re the champs for a reason,” Derrick White said. “They’re the champs until someone knocks them off. So they win games in many different ways and I think we’ve shown we can win games in many different ways.

“We just didn’t make the right play or enough plays to win it tonight. So obviously that’s something we can look back and learn from and grow from. And we’ve got a lot of time so we’ve just gotta grow from there.”

The matchup between the league’s best team and the league’s defending champion lived up to the hype. It was like a heavyweight boxing match as they went blow to blow in an intense, physical game, a duel that featured 13 lead changes. Kristaps Porzingis said it would not exactly be a measuring stick opportunity, but the Celtics will certainly arm themselves with plenty of lessons from this loss as they position themselves for a championship run.

“If we see them in the postseason, it’s going to be a big chess match,” Porzingis said.

Mazzulla was not discouraged by the performance. It came down to the final play. But it was hard not to feel like the Celtics missed an opportunity to put another stamp on how far they’ve come since last year. Down the stretch, it was reminiscent of painful losses in the past. They simply couldn’t get the ball in the hoop over the final five minutes.

The Celtics led by one entering the fourth quarter and had a prime opportunity with Jokic on the bench to begin the period. Tatum, who typically sits to begin the final frame, started the fourth. But the C’s couldn’t take advantage. Murray took over, scoring the Nuggets’ first seven points of the quarter. He couldn’t miss. He hit a turnaround jumper that put the Nuggets up 95-91 midway through the quarter.

The C’s responded with a 7-0 run ignited by a Derrick White 3-pointer to retake the lead at 98-95 with 4:51 to go. But, almost unbelievably, the Celtics’ offense went bitter cold. Jokic hit two consecutive shots as the Nuggets retook the lead, and they never gave it back.

Boston’s defense and ball security (three turnovers) kept them within a possession in crunch time but continued missing all their looks. Brown missed two free throws on one trip, and then the Celtics missed two 3-pointers when they got the offensive rebound. When Porzingis blocked a Jokic shot with 1:19 to go to force a shot clock violation, White then missed a 3-pointer.

With 23 seconds left, Aaron Gordon air-balled a 3-pointer and Tatum grabbed the rebound and took off in transition, but went one-on-four against Denver’s defense and missed the layup. Gordon was fouled and missed his second of two free throws, but a rare double lane violation was called. The Celtics won the jump ball, then called timeout with 13 seconds left. When their play call blew up, Mazzulla called another timeout with five seconds left. But Tatum’s game-tying shot attempt at the buzzer was way off the mark.

Boston made just one shot over the final 4:51 of the game – a Tatum dunk with 1:41 to play – but missed their other 10 shots in crunch time.

“I thought we got at the rim at will,” Mazzulla said of crunch time. “I’ll have to go back and watch it. I thought real-time, I liked the shots that we got, and I liked the spacing that we got.”

Other takeaways from the loss:

– Where would the Celtics be without White? His All-Star candidacy can be summed up with his play on Friday night, and specifically the third quarter. While the Celtics struggled to find their open shot and contain Jokic and Murray, White’s play on both ends in the third was pivotal in keeping the Celtics afloat and in front. He forced a steal that led to a fast-break floater over Jokic, and moments later drew a charge while scoring six consecutive points, including a three-point play that earned a kiss on the forehead from Porzingis. When he went to the line to shoot his free throw, White earned more MVP chants from the Garden crowd.

– The Celtics led by six at halftime but missed an opportunity to have a bigger lead. Behind a strong defensive second quarter, they led by 12 with less than four minutes remaining in the period but made just one shot – a Jaylen Brown triple in the final minute – to finish the half. The Celtics even grabbed five offensive rebounds on one possession but came up empty.

The C’s, after a hot start from deep, finished the first half 10-for-26 from long range, and finished 14-for-44 from distance.

– Tatum can’t get a break with the hanging-on-the-rim technical fouls.

The Celtics star was called for yet another one in the second quarter. After grabbing a steal, Tatum went coast to coast and flushed the ball with two hands. He swung through the dunk and propped himself up above the rim for an extra second – seemingly because Porzingis was underneath him – before being assessed a technical foul. He and his Celtics teammates voiced their displeasure as heavy boos rained down at TD Garden.

It briefly halted the Celtics’ momentum but didn’t completely ruin it as they went on a 9-1 run.