Boston Celtics coach Ime Udoka declared "the future is bright and we're just getting started" after the NBA Finals series defeat to the Golden State Warriors.

The Celtics led the Warriors 2-1 in the series before relinquishing fourth-quarter leads in both Game 4 and Game 5, and ultimately came unstuck in the penultimate match.

Stephen Curry registered 34 points (12-of-21 shooting, six-of-11 from three), seven rebounds and seven assists as Golden State recorded a 103-90 win in Game 6 to secure an unassailable 4-2 series lead.

That meant the Warriors lifted their fourth NBA Championship in just eight years, and seventh overall, as Boston's 14-year wait for an NBA Finals series win continued.

Udoka guided the Celtics to their first Eastern Conference title in 12 years, though, and he believes Boston have reason to be optimistic in the future.

"We learned a tremendous amount about each other as a staff and them learning what we wanted and vice versa. That's the message to the guys tonight," he said.

"This is just the start. A foundation has been set. We can kind of hit the ground running next year. Let's get healthy and all be on the same page.

"Now it's a matter of taking that next step. What I did say to the group was there are levels. You can see the difference in Golden State, a team that's been there, been together for a long time.

"The core group, it's been 10 years now. We've seen what we can achieve. It hurts we fell short of that.

"But what I did say is the future is bright and we're just getting started, so let's all come back better from this experience."

Udoka has experienced the pain of losing in NBA Finals before after he was an assistant San Antonio Spurs when they succumbed to defeat against the Miami Heat in 2013.

The Nigerian admitted the loss will hurt for a while, but called on Boston to use it is as a learning experience.

"It's going to hurt. It will hurt for a while. Probably that stuff never goes away. I've lost one before," he added. "That was part of the message. Let it propel us forward, the experience.

"Growth and progress that we made this season. Obviously, getting to your ultimate goal and falling a few games short is going to hurt. There are a lot of guys in there, very emotional right now.

"The message was we thanked them for the effort and the growth and everything they allowed us to do coaching-wise this year.

"The biggest message was learn from this, grow from it, take this experience and see there is another level to get to.

"Just don't come back the same as players, coaching staff. Let this fuel you throughout the offseason into next year.

"Let's not be satisfied. It's not guaranteed you're going to be here. The East is getting tougher every year. They'll come back better. We will as a staff as well."