CAMBRIDGE, Mass. –Brett Brown had a hard time sleeping Monday night.

It had a lot to do with the 76ers' 117-101 loss to the Boston Celtics that night in Game 1 of the Eastern Conference semifinals at TD Garden.

"We've lost twice since whenever," the coach said of the Sixers' second loss in 22 games before Tuesday's practice at Harvard's Lavietes Pavilion. "So we've been on a pretty good unusual run."

So only losing for the second time in as many games, is "your greatest joy or your worst misery," Brown said..  That's why he's trying to find a balance with the outcome.

"So you think about stuff all night long, as we should, as I should," he said. "It's just part of this time of the year, and part of the challenge, the excitement, in a sadistic type of way."

The disheartening thing about their Game 1 setback is the way they lost. The inspiration comes from knowing a lot of their misfortune was self-inflicted.

The Sixers will tell you that they didn't run their offensive sets properly. Nor were they physical enough or completed their assignments on defense.

Whatever the reason, the Celtics couldn't miss from long range, while the Sixers struggled to make anything from beyond the arc. Boston made 17 of 36 three-pointers (47.6 percent), thanks in large part to Philly's blown defensive assignment. In addition to giving up open looks, the Sixers missed 21 of 26 three-point attempts (19.2 percent). The Celtics also scored 23 points off Philly's 12 turnovers.

"Defensively, offensively. We didn't play at well at all," said Ben Simmons, who had seven of the turnovers.

Joel Embiid had a slightly different explanation  for their defensive shortcomings while watching film of Game 1.

"Defensively, I thought we didn't guard our own man," he said. "We didn't stick to the game plan. A lot of times we were over helping, especially me. So there's a lot of stuff we can definitely correct."

The Sixers – Embiid especially – enabled the Celtics to attempt a lot of wide open shots by focusing too much on help defense instead of staying on their assigned man.

A prime example of that came with the Celtics up, 97-88, in the fourth quarter. Al Horford and reserve point guard Shane Larkin orchestrated a pick-and-roll. JJ Redick, who was guarding Larkin, went under Horford's pick before picking up Larkin again.  Embiid also followed Larkin, leaving a wide-open Horford.

Larkin found the big man, who buried a three-pointer to put the Celtics up by 12 points with 5 minutes 32 seconds left.

"My job is to make sure that the ball stays in front of me," Embiid said. "Before the guard comes back and squares up, I got to go back to my man. I think next game, one of the adjustments will be just basically switching everything instead of letting [the Celtics] create some separation.

"That's basically all the guard is trying to do: Bait you into doing something."

As the Sixers found out, that's when Horford and Marcus Morris were able to get wide open.

"So I think next game, I think we got to honor the calls," Embiid said, "and we got to make sure we don't let them get any separations."

The Sixers were also doomed by an inability to keep the Celtics penetrators in front of them.  As a result, Boston kept attacking and taking advantage of mismatches following switches.  It got to a point where the Celtics were picking on reserve guard Marco Belinelli, who was a defensive liability.

Playing Justin Anderson more would be one option to correcting the defensive breakdowns. The Sixers defensive-minded reserve guard only played 5:16 on a night when Celtics point guard Terry Rozier (29 points) and small forward Jayson Tatum (28) torched his teammates.

But Philly will look to correct their defensive woes, horrid shooting and poor offensive execution before Game 2 on Thursday.

"We're fine," Redick said. "We got to be better. That's the bottom line.  We got to be better offensively and better defensively. There's no overreaction on our part."

Dario Saric agrees.

The power forward admits that the Celtics were the better team on Monday. He also realized that his squad was smacked around. However,  Saric thinks it would be crazy to expect the Sixers to record a sweep in each round of the postseason.

"But still we got the chance to beat them one time here," he said of TD Garden. "We need to execute what the coaches ask from us, and you know we will be on point."