Kyrie Irving defended his actions during the Brooklyn Nets' 115-114 loss to the Boston Celtics on Sunday, where he appeared to raise his middle finger to fans on two separate occasions during Game 1 of their playoffs opener.

Irving, who played for Boston for two turbulent seasons before a sour exit in 2019, has been regularly booed by fans at the TD Garden, and the ill-feeling has only intensified with each meeting.

The 30-year-old has not hidden his feelings towards the organisation either, stomping on the Celtics logo at mid-court of the Garden following Brooklyn's win in Game 4 of last season's playoffs series between the two.

Scoring a game-high 39 points during his running battle with the crowd in Sunday's loss, Irving asserted he is only reciprocating the ill-sentiment.

"Look, where I'm from, I'm used to all these antics and people being close nearby," Irving said post-game. "It's the same energy, and I'm gonna have the same energy for them.

"And it's not every fan. I don't want to attack every fan, every Boston fan, but when people start yelling 'p****' or 'b****' or 'f*** you' and all this stuff, there's only but so much you take as a competitor.

"We're the ones expected to be docile and humble, take a humble approach. F*** that, it's the playoffs. It is what it is."

The seven-time All-Star relentlessly attacked on Sunday, playing with notable vigour on his way to 39 points, six assists, five rebounds and four steals in just over 42 minutes.

He also shot 60 per cent from the floor in both total and three-point categories, hinting that he was driven by the crowd.

"Embrace it," Irving said. "Embrace it. It's the dark side. Embrace it.

"I know what to expect in here, and it's the same energy I'm giving back to them. This isn't my first time at TD Garden so what you guys saw, what you guys think is entertainment, or the fans think is entertainment, all is fair in competition."