NEW YORK (AFP) -- Adding All-Star guard Jrue Holiday and Latvian big man Kristaps Porzingis has given the revamped Boston Celtics new belief they can contend for their first NBA crown since 2008.

The Celtics have lost in the Eastern Conference finals in four of the past seven seasons as well as being defeated by Golden State in the 2021 NBA Finals.

But two major off-season deals have changed the lineup around core stars Jaylen Brown and Jayson Tatum to provide new confidence in another title run, the latest move coming for Holiday on Sunday.

"As a competitor, he's an assassin," Brown said of Holiday.

Celtics president of basketball operations Brad Stevens calls Holiday a "perfect fit" for the Boston roster, adding, "We're trying to win a championship. We're trying to be as good as we can be."

Porzingis, a 7-foot-3 (2.21m) forward, was obtained in a three-team deal that sent guard Marcus Smart to Memphis.

"Extremely excited understanding the opportunity we have here," said Porzingis.

"Expectations are high. We realize what we want to achieve. It's going to be in our hands to do that daily work to get that end result. But we have to focus on the day to day results and then we'll get there.

"Everybody is at a certain point in their career where we are coming together here for one goal. That's going to make all of that process of playing together so much easier.

"Sooner or later we'll find it and hit that rhythm and we'll be fine."

Holiday was acquired from Portland on Sunday for 2023 NBA Sixth Man of the Year Malcolm Brogdon, Robert Williams and two first-round NBA Draft picks.

"Two picks, two good players, that's a real price, but that's how good we think Jrue is," Stevens said. "You got to pay a good price for things."

That trade came four days after Holiday went to the Trail Blazers from Milwaukee in the deal that sent Damian Lillard to the Bucks and pushed the Celtics to add more talent to contend in the East.

"Jrue is fantastic. I have a tremendous amount of respect for Jrue," Brown said of his new teammate. "He plays with a certain force you can just feel. He's just super solid.

"To be playing alongside him, I think, will be a tremendous honor."

Tatum and Holiday were teammates on the US gold medal team at the Tokyo Olympics.

"Excited about Jrue," Tatum said. "He's one of the most well-respected guys in the league. Great talent on both ends. Champion."

But Tatum warns that with championship dreams unfulfilled in Boston, there will only be working holidays for the Celtics.

"We should all feel like we've got to do a little bit more because we didn't win," Tatum said. "Whatever we've done has been great but it hasn't been enough.

"Everybody has to sacrifice but be willing to do more, if it's going from eight rebounds a game to 11, whatever it is, we've all got to be willing to do more because we haven't accomplished what we're trying to do.

"I'm looking forward to doing more. So should everybody else."