CAMBRIDGE, Mass. — There is no doubt about it: Defense was the main problem for the Sixers in their 117-101 loss to the Celtics on Monday night.

That's the first place Brett Brown's mind went when evaluating what went wrong, and Joel Embiid was the first person to agree.

"Defensively, we were trash," Embiid said Tuesday before the Sixers practiced at Harvard University.

On offense, things weren't great, either. Embiid went on to say the Sixers were off and missing open shots, and that Thursday's Game 2 would be different.

It's true that the Sixers missed a lot of open looks. It's not out of character for them – at least in the playoffs.

The Sixers were 19 of 48 on uncontested shots Monday night. At 39.6 percent, that's not great. Compared with the Sixers' performances in their six playoff games so far, it's middle-of-the-road: Only in Game 1 (26 of 46, 56.5 percent) and Game 3 (22 of 43, 51.2 percent) against Miami did they have a better percentage on uncontested field goals.

76ers uncontested field goals in the playoffs
Game 1 vs. Miami 26 46 56.5
Game 2 vs. Miami 16 53 30.2
Game 3 at Miami 22 43 51.2
Game 4 at Miami 15 43 34.9
Game 5 vs. Miami 19 49 38.8
Game 1 at Boston 19 48  39.6

Additionally, the Sixers have been struggling from beyond the arc in the postseason, whether contested or not: They've shot better than 25 percent only twice in six games, with their worst performance coming in Monday's Game 1 loss.

76ers 3-point performance in the playoffs
3PtA 3PtM 3pt%
Game 1 vs. Miami 18 28 64.3
Game 2 vs. Miami 7 36 19.4
Game 3 at Miami 18 34 52.9
Game 4 at Miami 7 31 22.6
Game 5 vs. Miami 7 28 25.0
Game 1 at Boston 5 26 19.2

"I think if we make a couple more threes and we get a couple more stops, with the effort offensively that I gave, I think we're going to be in a good place on Thursday," Embiid said.

That might be the more truthful statement.

The Sixers attempted only 26 three-pointers, the fewest they've tried so far during their six postseason games. The Celtics deserve some credit – Boston's defense worked exactly as it planned – but the Sixers' offense did not do what is necessary: passing the ball, setting good screens and creating movement.

Embiid, who finished with 31 points, might benefit from the attention that's being paid to the Sixers' perimeter players.

"Schematically, Boston is always mindful of the three-point shot, and in some ways they seem quite OK to let Joel get 40," Brown said.

After Monday's game, Celtics coach Brad Stevens said you have to pick your poison when you play the Sixers. It served the Celtics well by choosing to go heavy on perimeter defense. But that means there's one person often left open at the three-point line – Embiid.

"The coaches want me to take about eight to 10 threes a game, but I would never – that's not happening," Embiid said. "I'm going to be open, and I can make those, but I don't feel comfortable, that's not my game. … Sometimes I have a tendency to pump-fake for no reason; that just shows you that I don't want to be that guy."

Brown laughed and playfully argued with Embiid that the number was four to six, not eight to 10. But Brown did say the coaching staff would like Embiid to be more aggressive from deep.

"He's right. I think in the trail spot he's really good at it. It's harder with a mask and it's harder when you haven't played basketball," Brown said. "I mean look at [Al] Horford. Look at what a five-man can do that can shoot threes. But in general, we need to shoot more threes as a team, and if that's including Joel in that trail spot especially, fine."

On Monday, the Sixers seemed out-of-sorts on both sides of the ball. They need to attempt more three-pointers, and to do that they need to work through the offense and not let Boston bully them into iso-ball.

But if the shots aren't falling, as has been the case throughout most the playoffs, it is the defense that will have to pick up the slack.