CAMBRIDGE, Mass. — Joel Embiid has always been a straight shooter, and what he said at Tuesday's 76ers practice is just the latest example.

The Sixers' center was asked what he saw on video of Monday night's 117-101 loss to the Boston Celtics.

"Defensively, I thought we didn't guard our own man," Embiid said of Game 1 of the Eastern Conference semifinal at TD Garden. "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 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. Joel Embiid followed Larkin too, leaving Horford wide open.

Larkin found the big man, who buried a three-pointer to put the Celtics up by 12 points with 5:32 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, "and we got to make sure we don't let them get any separations."