BOSTON — The Nets got a bitter taste of a Celtics playoff crowd in Friday’s Game 3 loss, and that was with TD Garden at one-quarter capacity.

Sunday’s Game 4 is going to be at near full capacity and a whole different atmosphere than they’ve experienced in years.

“I don’t know how many people were in the arena [Friday], but I know it wasn’t full but it was still good atmosphere and loud. And we expect it to be pretty crazy [Sunday],” Joe Harris said. “But you still find a way to communicate with one another, make sure that you’re not letting it become too much of a factor.

“We’re obviously excited. This is what playoff basketball is all about, the atmosphere. Brooklyn, the Barclays was incredible, and [Sunday] night will be an awesome atmosphere as well.”

There were “just” 4,789 at TD Garden on Friday. There could be close to four times that in Game 4, and they’ll be at full froth will the Celtics having a chance to even the series at 2-all.

“I can’t f—ing wait until Sunday — 17K, green, I’m going to see the leprechaun, I can’t wait. That’s what Boston is all about, that’s what the fans are about. They are going to give us that life, that juice, that energy,” Celtics big man Tristan Thompson said. “They haven’t seen us all in this arena in a long time, so I know everyone is excited. I can’t wait.”

This will be by far the biggest crowd the Nets have faced all season, by a multiple. They played in Miami on April 18 under fairly lax restrictions, but that was still capped at 5,700 and a regular-season game. Home-court advantage in a playoff game is a different animal.

“There’s a reason why people play for home court all year,” Brad Stevens said.

Jeff Green (left plantar fascia strain) and Spencer Dinwiddie (partially torn ACL, right knee), with the former not expected to be reevaluated until at least a week from Sunday.

Shot-blocking Celtic Robert Williams III (turf toe) is doubtful, while Kemba Walker (left knee medial bone bruise) will be evaluated Sunday morning.

“Kemba was sore,” Boston coach Brad Stevens said. “I think that he’ll go through stuff in the morning tomorrow and have a better idea on him.

“Rob’s doubtful. He probably won’t do anything in the morning and see how he feels as we get closer to game time. But [Friday] night, even in his stint, I thought he looked pretty limited. So we’re hopeful to have everybody available, but at least in Rob’s case I’d say that’s probably doubtful.”

The Nets will have limited non-vaccinated tickets available for Tuesday at Barclays Center, The Post has learned. Game 5 will be at 7:30 p.m. and air on TNT.

If Game 6 is necessary, it will be Thursday at 7:30 pm on TNT.