In the first three games of their Eastern Conference semifinals with the 76ers, the Boston Celtics showed tremendous poise in storming to a 3-0 series lead.

While the Sixers still have a huge mountain to climb, Boston wasn't able to kick them to the curb after their 103-92 win Monday night at the Wells Fargo Center.

And a major reason was that the normally composed Celtics played out of character.

They were undisciplined on the court, forcing shots on offense, and leaving Sixers shooters open too frequently while also committing 15 turnovers compared to the Sixers' eight.

When it was suggested that Boston lost its poise, Celtics coach Brad Stevens said they were guilty as charged.

"Yes, but I thought that had a lot to do with Philly," Stevens said. "Philly did a great job, they pounded on us, were very physical and tough. Hats off to them."

Celtics forward Marcus Morris wouldn't admit that they lost their poise.

"No, I thought we got in foul trouble because guys got in foul trouble and when that happens, you play differently," said Morris, who had 17 points and five fouls.

The Celtics were assessed 28 fouls, by far their most in this series. Their previous high in this series was 21. The Sixers were called for 23 fouls.

With the foul trouble came more than usual yapping by the Celtics at the officials.

More of a factor than the fouls was the intensity with which the Sixers played.

"We didn't match their effort," said point guard Terry Rozier, who was limited to 11 points after scoring 29, 20 and 18 in the first three games. "That is a problem when you don't match a team like the 76ers' effort."

The captain of the all-tough team for Boston is the 6-foot-1, 190-pound Rozier, who takes no guff from anybody, even somebody a foot taller.

Late in the second quarter after Rozier was called for an offensive foul after elbowing JJ Redick, Sixers 7-foot-2 center Joel Embiid tried to take the ball from him. Rozier took exception and pushed Embiid in the chest and the two appeared to be headed for blows before order was restored.

"I set the record straight, I wake up every morning worried about nobody, no man on this earth," Rozier said when asked about the incident with Embiid. "We were out there having fun and it was part of the basketball game, and that is all it is."

A double technical was called on them. That seemed to rile up the Sixers, who were leading 40-38 at the time.

The Sixers took a 47-43 lead into halftime, but that was before Boston truly got unglued.

Not so coincidentally, Boston lost its composure the most at the time the Sixers broke the game open late in the third quarter.

After Rozier made a driving layup to cut the Sixers lead to 66-62 with 3 minutes and 34 seconds left in the third quarter, the Sixers went on a 10-0 run.

Included in that run were two technical foul shots by Marco Belinelli after the Celtics' Jaylen Brown and Stevens were assessed T's.

It summed up a frustrating evening for Boston.

Whether the Celtics lost their poise wasn't a concern to Rozier in the least.

"We lost the game; whether we lost our cool, you can use a million excuses," Rozier said. "They played better than us, played harder than us."