The Boston Celtics' typically straight-faced basketball boss Brad Stevens couldn’t hide his smile after watching just one practice with Jrue Holiday on the team.

“We made a thousand mistakes. But you could also see, like, there’s that thing that’s there,” Stevens said at an introductory news conference on Wednesday, three days after the Celtics traded for Holiday. “There’s a togetherness. There’s an excitement. There’s a joy, a competitiveness.

“And I think he brings it as well as anybody around," Stevens said. "I just think that’s contagious.”

The Celtics acquired Holiday on Sunday from Portland, where he had been sent as part of the trade that moved Damian Lillard to Milwaukee. The deal came together on Sunday, the night before training camp opened, and Holiday sat out Tuesday's practice and watched.

A day later, with Celtics Hall of Famer Paul Pierce as a spectator, Holiday joined his new teammates at their practice facility and set a tone that the team hopes will result in a championship.

“There was just an electricity in the gym today,” co-owner Steve Pagliuca said. “Paul Pierce turned to us and said he’s never seen an NBA practice in his whole entire career, that they went that hard, that fast for that long.”

Although they are tied with the Los Angeles (and Minneapolis) Lakers with an NBA-best 17 championships, it’s been 15 years since the Celtics hung their last banner in TD Garden. They have reached the Eastern Conference finals five times in the last seven seasons — making it to Game 6 of the NBA Finals two years ago — but they seemed to be getting no closer to another title.

So in an offseason upheaval, Stevens traded point guard and defensive star Marcus Smart for Kristaps Porzingis, gaining an All-Star big man but giving up the player who was the emotional heart of the team.

In Holiday, they believe they’ve filled that gap. It cost them point guard Malcolm Brogdon, the NBA’s reigning Sixth Man of the Year, and forward Robert Williams along with two first-round draft picks, but with Holiday joining All-Stars Jayson Tatum and Jaylen Brown, Boston joined Milwaukee as 19/5 favorites to win it all, according to FanDuel Sportsbook.

“We’re adding everybody we can who will add character, commitment and extreme talent. We’re also, unfortunately, letting some of those guys go,” co-owner Wyc Grousbeck said. “We’re doing absolutely everything we can. But if you’re in Celtics ownership, that’s what you do. Or you make way for somebody else.”

Holiday started his career in Philadelphia, spent the next seven years in New Orleans and then moved to Milwaukee in 2020-21, joining with Giannis Antetokounmpo to win an NBA title his first season there. The next year, the Bucks lost to Boston in seven games in the Eastern Conference semifinals, and Holiday noticed something about the city and its fans.

“The fans are literally insane, and I’m proud to be a part of that,” said Holiday, who grew up in Los Angeles as a Lakers fan. “I know a lot of my family’s probably hurt, but I know this is a blue-collar town. They love people that work hard and they put their heart into it. And that’s just the type of person that I am, is every time I step on to the court, I give them everything.”

That was a hallmark of Smart's career in Boston, too. The three-time member of the all-defensive team and 2022 Defensive Player of the Year was beloved in Boston — more for his effort than as an offensive threat who averaged 11.5 points and 6.3 assists last season.

Holiday averaged 19.3 points, 7.4 assists and 5.1 rebounds last year, while matching Smart's 1.5 steals. Grousbeck made sure to note that, in addition to his two All-Star selections and his five appearances on the all-defensive team, Holiday is a three-time winner of the NBA’s teammate of the year award.

He is also under contract for two more seasons, but Stevens said they will begin talking about an extension as soon as they are allowed. The deal put Boston over the salary cap’s new “second apron” that comes with increased penalties for big-spending teams.

"We haven’t blinked at all,” said Grousbeck, who was part of the ownership committee that worked on the restrictions. “I’m aware of all that. We’re going to be over the second apron and paying those penalties. and that’s the way life is.

“It’s designed so that we can have more competition. We're fine with competition," he said, "as long as we win.”

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