BOSTON -- The Celtics pride themselves on being the more physical team in every game they play. It's something coach Ime Udoka has made a point of emphasis since taking over as the team's coach last summer, and has played a huge part in Boston's massive midseason turnaround.

But through three games of these Eastern Conference semifinals, the Celtics have allowed the Miami Heat to dictate the terms of engagement when it comes to aggression and physicality in this series. And, when the Heat have had success getting into the Celtics, the results have been ugly: a 39-14 drubbing in the third quarter of Game 1, and a 39-18 shellacking in the first quarter of Game 3

Those 24 minutes have fueled Miami's rise to a 2-1 lead in this best-of-7 series heading into Game 4 here at TD Garden Monday night. And, as a result, the Celtics know they are going to have to match Miami's intensity moving forward if they want to advance out of this series and return to the NBA Finals for the first time since 2010.

"We just had a good session that we looked at how physical they were, how aggressive they were at the start of the game," Celtics coach Ime Udoka said after Boston's practice Sunday afternoon. "We were kind of caught off guard by that. But I could have done a better job coaching us, preparing us for that. I mentioned it quite a few times, but the team did as well.

"Miami, historically, since I've played against them for 10-plus years now, is they try to go harder and try to be more physical, and it wasn't a bunch of adjustments. It's increasing their physicality ... Marcus mentioned it before the game, Al mentioned it, I mentioned it, and so it was a little disappointing to get caught off guard like that with us knowing that's really what they're gonna go to, what they went to in Game 1. So something we have to get better at. We saw what they did, similar things we do to other teams, and ways for us to attack that and kind of combat some of their aggressiveness."

The fact that the third quarter in Game 1 and the first in Game 3 are the only ones the Heat have won in this series is irrelevant. What is relevant, however, is how Miami won those quarters. Both times, the Heat got into the Celtics physically. They made Boston uncomfortable. They forced the Celtics into quicker decisions than they would like.

And, as a result, the Heat were able to force one turnover after another -- allowing them to get out in transition and boost their offense, which, given Miami's weakness in half court offensive sets, is vital to the Heat's chances of winning this series.

In Game 3, those turnovers turned into a staggering 33 points, in part because the Heat were able to generate an insane 19 steals. Miami's ability to do so goes right back to the same issue: Boston allowed Miami to completely disrupt how it wants to play, with disastrous consequences.

"I think it's just being smart," Celtics guard Payton Pritchard said. "When we're driving, play off two feet. They had 19 steals, so it was a lot of live-ball turnovers. So we can just limit those and I think we'll be all right."

When the Celtics have limited those in this series, they have been more than all right. But the times they have not been able to do so have been so costly that they find themselves trailing 2-1 in the series for a second straight round, and are once again alternating wins and losses with an opponent after doing so for the first six games against the Milwaukee Bucks in the Eastern Conference semifinals.

The difference this time around? Miami, as the East's top seed, has home court. So if the Celtics can't figure something out in Game 4 to mitigate Miami's physicality edge, they could be heading back to the shores of Biscayne Bay with their season on the line in Game 5.

"Stay level-headed," Williams said, when asked how the Celtics have managed to survive the peaks and valleys of the playoffs so far. "At the end of the day, no matter what happens, whether it's a big win or big loss, you have to play it the right way. We can't let it carry over. It's 2-1 right now and we play in front of our Garden fans and can make it 2-2.

"It's one of those things where we still control our destiny. We have to come out there and not only be a little more physically dominant and be more conscious of what we are trying to accomplish. Just like a regular season, there's going to be peaks and valleys, you are going to have success and times you are not playing well but the best teams stick together through thick and thin and they do their best job understanding the same thing can't beat you twice."

Boston also spent time Sunday finding ways to get Jayson Tatum more involved. Tatum, who went just 3-for-14 in Game 3, only took four shots in the second half, and made none of them.

Udoka said doing so requires a combination of both trying to get Tatum off the ball looks more often, allowing him to get away from Miami's physical defenders -- led by PJ Tucker -- and also him continuing to make strides in his playmaking as he has this season to trust his teammates to make plays and shots themselves. And, when they do, opportunities will come back around for Tatum to do the same.

"Off-ball actions always have worked well for him, whether he's a screener or some flares and things like that because they are loading up on him every time he has the ball, but also understanding that they're guarding him like this," Udoka said. "He's had huge playoff series so far. Teams are going to come after him, so for him, it's looking to get guys involved early as he makes those passes and makes those reads, the defense always loosens up on him and he can get going himself."

The Celtics will also have to attempt to even the series while navigating a few injuries. Marcus Smart, who briefly left Game 3 with a right ankle sprain, experienced some swelling in his ankle Sunday, Udoka said, and the team will see how he responds to treatment throughout the day, and how it looks Monday ahead of the game.

The same applies to center Robert Williams, who missed Game 3 with knee soreness that Udoka said would have Williams on a "day-to-day" basis throughout the remainder of the playoffs. Udoka did say Williams felt better Sunday, but that treatment and response to it would determine whether he could go in Game 4. Tatum, meanwhile, was fine after briefly leaving Game 3 with his own shoulder stinger in the fourth quarter.