The first loss of the year was always going to come for the Celtics, but man was it a frustrating one, as the Celtics blew a 19-point lead and lost their cool on the way to a 120-102 final in Chicago on Monday night.

On the board with 35 of the first 51 points of the game, the Celtics looked set for a runaway victory at the United Center, but a Nikola Vucevic layup marked the start of what was an absolutely wild run by the Bulls.

Beginning with the Vucevic layup, the Bulls went on to outscore the Celtics by an absurd 49-19 mark until the halftime horn mercifully sounded for Joe Mazzulla’s squad.

But it was just the start of their problems.

Frustrated with the lack of a technical foul on the Bulls for a similarly emotional expression that got Jayson Tatum hit with a technical, Mazzulla was hit with technical, and then ejected mere seconds later for barking at the officials. Mazzulla’s expression really sort of said it all when it came to his ejection.

“I just have to have better composure under those circumstances,” Mazzulla, who left head coaching duties to Damon Stoudemire following the ejection, said after the loss. “I was just trying to get the referee’s attention.”

No matter Mazzulla’s intentions on the sequence that got him tossed, it was painfully clear that the Celtics weren’t going to catch any breaks from the officials in this game, and Grant Williams didn’t help.

Frustrated after he was hammered on back-to-back plays, Williams exploded off the floor after he was whistled for a shooting foul, and made contact with referee Cheryl Flores.

Flores immediately called Williams for a technical, and hit him with an ejection.

Beyond the nonsense, the Celtics were led by Jayson Tatum and his 26 points behind an 8-for-18 shooting performance, including makes on four of his eight tries from behind the arc.

With another performance of at least 25 points to his name, Tatum became the first Celtic since Paul Pierce in 2005 to score at least 25 points in the opening four games of the season.

DeMar DeRozan led the way for Chicago, with 25 points on a 10-for-17 night from the floor, while Vucevic dominated 18 points and a staggering 23 rebounds in almost 31 minutes of action.

The Celtics will return to action Friday night against the Cavaliers.