CHICAGO -- "The worst defeat in Chicago Bulls franchise history" sounds bad, but it looked even worse.

Boos rained down from the United Center crowd as the Boston Celtics slaughtered the Bulls 133-77, with the 56-point margin of defeat being the largest in the 53-year history of the franchise.

Afterward, the Bulls didn't hide their embarrassment:

Rookie center Wendell Carter Jr. went straight to the weight room to lift; Carter lost eight games at Duke, and has now lost 21 with the Bulls.

A deflated Zach LaVine addressed reporters briefly, clearly chagrined about substitution patterns that saw Chicago's starters benched for long stretches.

Lauri Markkanen, who made the final go-ahead field goal in Chicago's win Friday night against the Oklahoma City Thunder, flatly admitted that the Bulls starters "deserve" to be pulled given their slow start and poor shooting.

Jim Boylen, coaching only his third game for the Bulls after Fred Hoiberg was fired, repeatedly told reporters that he was "disappointed" by the "embarrassing effort."

"We don't have that internal toughness yet to play at this level consistently," Boylen said.

The Chicago Bulls' starting five were yanked at once in both the first and third quarters of Saturday night's dubious loss against the Boston Celtics. Tannen Maury/EPA

It got ugly fast.

Three-point attempts by Markkanen and Justin Holiday clanked off the front rim. Even after Boylen yanked all five of his starters the first time with 7:15 left in the first quarter, the Celtics continued to build a 17-0 lead. Jabari Parker, who came in with the Bulls' second unit, finally got Chicago on the board with a pair of made free throws with 5:42 left in the first quarter. That was the latest into a game this season before a team scored its first points.

Chicago didn't make its first field goal until nearly seven minutes into the game and the Bulls trailed by 21 points at halftime.

"I felt embarrassed," LaVine said of the group benching after the game. "I wish I was out there competing."

Boston's lead only snowballed in the second half.

Midway through the third quarter, Chicago had fallen behind by 32 points. Boylen pulled his starters simultaneously with 9:02 left in the third quarter, and that was it for Ryan Arcidiacono, LaVine, Holiday, Markkanen, and Carter.

"I think your play is embarrassing," Boylen said when asked if he thought the mass substitutions were done to embarrass the players. "... I worked for [San Antonio Spurs head coach] Gregg Popovich. He subbed five guys a ton of times. Nobody says a word to him about it. He felt that was best for the team. I felt that was best for the team where we were at.

"I wanted to give the other guys a chance to see if they could right the ship a little bit," Boylen continued. "If I don't like the five guys out there, if I don't like the combination, I'm going to look at a new combination. Take them all out, let them sit there and think about it."

Largest Road Wins - NBA History Margin Opponent Sat. Celtics 56 Bulls 1986 SuperSonics 56 Rockets 2003 Pistons 52 Pistons 2015 Spurs 51 76ers >> Regular season only

The Bulls starters had a combined 27 points Saturday, the fewest for a Bulls starting lineup since Nov. 10, 2007 against the Raptors.

On the flipside, Boston started third-stringer Daniel Theis at center with All-Star Al Horford (knee) and top reserve Aron Baynes (ankle) unavailable because of injury. All Theis did was score 22 points, grab 10 rebounds, block 4 shots, and compile a plus-minus of plus-50 in 33 minutes. That's the best plus-minus in a game by a Celtics player over the past 20 seasons, and the best by any player this season, according to ESPN Stats & Information.

Chicago's reserves played the final 21 minutes, and yet the Celtics continued to run up the score. With a little more than eight minutes left in the third quarter, Boston's lead had swelled to 42. By the three-minute mark, Boston led by 52. Eight different Celtics players sank at least two 3-pointers Saturday night, the most in a game in NBA history. Former Boston starter Jaylen Brown had a game- and season-high 23 points off the bench in 29 minutes, making all three of his 3-point attempts and 8-of-11 from the field overall.

Even as the clock ticked down, the Celtics continued to roll up the score to win by 56 points -- the largest margin of victory in franchise history.

Meanwhile, the United Center crowd became more restless. The jeers were getting louder, fans started exiting the building and the loudest cheers came from the free hot dogs being thrown by the in-game entertainment staff. After the final buzzer, the remaining fans loudly booed the Bulls -- who fell to 6-21 -- off the court.

"That happens in the NBA sometimes," LaVine said. "We responded in the second quarter. I don't know. I do not know. There's a lot of questions you could ask, but I really don't know."

The Bulls don't have much time to find answers. They have to return to the United Center on Monday to host the Sacramento Kings.