Brooklyn Nets star Kevin Durant believes "thinking too much" is partly to blame for his struggles in the NBA playoffs against the Boston Celtics.

The Celtics extended their series lead in the Eastern Conference first round to 3-0 after a 109-103 victory at Barclays Center, and Durant was again unable to do much about it.

Despite averaging 29.9 points per game during the regular season, Durant is averaging just 22.0 in three postseason games and only scored 16 in his latest outing on Saturday.

Bruce Brown was the highest scorer for the Nets with 26 points on 10-of-19 shooting, but he and Durant contributed to 10 of the team's 18 turnovers.

"I was just thinking too much to be honest, this whole series," Durant said after the game. "Like how I approach the game. We got another game to play, another opportunity, and I'm looking forward to that.

"I feel like the first two games I was trying to be too aggressive. A team that's loading up on me, that's trying to take me out of all my actions."

A starring role from Jayson Tatum was the difference for Boston as the 24-year-old scored 39 points, with six assists and five rebounds, while Robert Williams returned from injury to play 15 minutes and help stifle Durant and Kyrie Irving, who himself also managed just 16 points.

"Every team I've been on, you're just trying to figure out the best way to play," Durant added. "When you got good team-mates around you as well, you're trying to figure out, I try to figure out how I can be the best version of myself and also not getting in my teammates' way.

"Sometimes I think too much about it. Sometimes I need to go out there and just [have] no thoughts in my head and just play.

"I feel like I prepared myself the right way. It's a matter of the small decisions in the game that may not go in my favour. I thought I found my teammates better than I did the last two games. I just need to score more."

The Nets must win Game 4, which takes place at Barclays Center on Monday, to keep the series alive.