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The Celtics exude a sense of familiarity and confidence with Porzingis back on the court.

Kristaps Porzingis is back. And so too are the championship-level Celtics.

Porzingis’ surprise return lived up to every bit of the hype. From a goosebump-inducing walkout from the Celtics locker room, to the anticipatory rumble inside TD Garden when Porzingis emerged from the tunnel, to the full roar when the 7-foot-2 big man threw his arm skyward to acknowledge the crowd.

With a final swig of his double espresso, Porzingis hit the parquet and immediately helped the Celtics serve notice to the rest of the league that this team truly is the favorite to repeat as NBA champions.

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It feels weird to say that, on a team overflowing with talent -- including All-Stars Jayson Tatum and Jaylen Brown and the All-Defense tandem of Derrick White and Jrue Holiday -- Porzingis is the most important piece. Maybe it’s better to suggest that he's more like the final infinity stone, the one piece that transforms the Celtics from great to something that often feels untouchable.

The numbers suggest the Celtics are just fine without Porzingis. Boston owns an .833 regular-season winning percentage when Porzingis has been sidelined (35-7 last season including playoffs; 14-3 this year). That mark actually dips to .758 when he’s on the court, having posted a 44-14 record with him in the lineup.

But the eye test tells a different story.

The Celtics are just a different beast with Porzingis on the court, from the rim protection that seemingly unlocks a different level of defensive aggression to his offensive versatility that makes a historic Boston offense even more difficult to defend.

Consider this: Boston ranked 24th in the NBA while allowing opponents to shoot 65.6 percent inside five feet in its 17 games this season without Porzingis. That number plummeted to 51.5 percent in Porzingis’ debut against the Clippers. Boston is able to gamble more with Porzingis on the back line, and that manifested itself in a combined 21 steals and blocks, the second highest stocks output of the season for Boston (22 stocks in a 30-point win over the Hawks).

When the Celtics erupted for 51 points in the second quarter while tying an NBA record with 12 3-pointers, you could feel the air come out of a Clippers team that had won five straight and was playing some of the NBA’s best defense this season. Even with Porzingis on the bench, Payton Pritchard and Sam Hauser took turns peppering the Clippers with triples in a quarter that brought back a lot of memories of Boston’s dominance a season ago.

The final score was a 126-94 shellacking of the Clippers in Porzingis’ return. The real result was a firm message to the rest of the league that the champion-level Celtics are back, too.

Not that they ever really left. Boston was cruising at 14-3 including a signature win last week over the previously undefeated and Eastern Conference-leading Cleveland Cavaliers. But the Celtics hadn’t quite looked like the team that steamrolled opponents for much of last season, then rumbled their way to a 16-3 record in the postseason.

Porzingis was huffing and puffing early but showed less rust than you might imagine after a five-month rehab from ankle surgery. He finished with 16 points on 6-of-12 shooting (he was 5 of 6 from inside the arc) to go along with six rebounds, two blocks, two assists and a steal over 22:37.

There is simply a joy when Porzingis is on the court that permeates this team. The Celtics are not adverse to fun, regardless of player availability, but from Derrick White checking his pockets for 3s after his fifth trifecta of the night to Al Horford screaming, "Pritch please!" after Pritchard made one of his six triples, the Celtics wore Porzingis’ perma-grin throughout Monday’s tilt.

With Porzingis back in the lineup, the Celtics oozed a familiar machismo.

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It's not always going to look as good as it did in that dominant second frame. The start of the third quarter showed that Boston is still more than capable of losing its focus for a maddening amount of time. But the Celtics caught themselves and tore the game open yet again.

If the rest of the NBA was hoping that the Celtics might fall victim to a championship hangover, Porzingis’ return might just be Boston's IV therapy. After bringing back virtually the same roster from a season ago, the Celtics were always a threat to repeat. Their play on Monday night was a reminder that the gap between them and other contender might just still be a chasm.

It’s hard to watch this team and not wonder how an opponent can possibly beat them four times in a seven-game series. There’s just too much talent. Boston must stay healthy -- with Porzingis at the top of that preservation list -- but his return gives the team a jolt at a point in the calendar when it would have been easy to get caught daydreaming.

Porzingis’ return hit like his beloved double espresso Monday night. The Celtics felt whole again, even while playing without the backup big man combo of Horford and Luke Kornet.

There are still plenty of steps to get back to where they want to go. But getting Porzingis back was a big one. And it sure feels like these Celtics are still many steps ahead of the pack early in the NBA calendar.