The Boston Celtics have acquired All-Star point guard Kyrie Irving from the Cleveland Cavaliers for point guard Isaiah Thomas, forward Jae Crowder, center Ante Zizic and Brooklyn's 2018 unprotected first-round pick, the teams announced Tuesday night.

Irving, 25, requested a trade during a July meeting with Cavaliers owner Dan Gilbert. At the time, Irving said that he wanted to play in a situation in which he could be more of a focal point and that he no longer wanted to play alongside LeBron James, sources said.

Tuesday night, in response to a fan's video on Twitter thanking Irving, James tweeted:

That's the only way to be to the kid! Special talent/guy! Nothing but respect and what a ride it was our 3 years together Young Gode #Filayy https://t.co/wKYmYsmdgG — LeBron James (@KingJames) August 23, 2017

Celtics president of basketball operations Danny Ainge noted the bittersweet nature of Tuesday's trade.

"This has obviously been a roller coaster of a day for us, trading away Isaiah and Jae and Ante, especially Isaiah and Jae, who have been such a big part of our team and our success and our Celtic culture as leaders of our team. Very, very difficult day," Ainge said. "At the same time, a very exciting time [to add] one of the best offensive players in the league."

Ainge said that it was a very tough phone call to inform Thomas, who had emerged as the face of the franchise since he arrived at the trade deadline in February 2015.

Ainge also said the Celtics did their homework on Irving after his falling out with James in Cleveland and said Irving is "excited" to be joining the Celtics. Ainge also acknowledged that Irving's price tag was high.

"It is a high price tag," he said. "But acquiring a 25-year-old perennial All-Star, a player that fits a timeline for us and is a fantastic offensive player, one of the best offensive players in the league, you have to pay a heavy price."

Pressed on the difficulty of giving up the unprotected Brooklyn pick, Ainge noted, "We valued it from the time we got it, and it's still very valuable. Obviously, we value Kyrie more. It's that simple."

Irving has three years and $60 million left on his contract, but he can opt out of the final year before the 2019-20 season. The Celtics posted on Instagram that Irving will wear No. 11, as his familiar No. 2 is retired in Boston for Red Auerbach.

All-Star Goodbyes Six players who were selected as All-Stars in the 2016-17 season have switched teams this summer, the most ever in one NBA offseason. Old Team New Team Jimmy Butler Bulls Wolves Paul George Pacers Thunder Gordon Hayward Jazz Celtics Kyrie Irving Cavaliers Celtics Paul Millsap Hawks Nuggets Isaiah Thomas Celtics Cavaliers -- Elias Sports Bureau

Thomas, 28, led the Celtics to the best record in the Eastern Conference last season, averaging 28.9 points and 5.9 assists over 33.8 minutes per game during the regular season.

Thomas has spent the offseason recovering from a right hip injury that kept him out of the final three games of the Eastern Conference finals. He opted not to have surgery.

Ainge said Thomas' injury did play "some" into his making the deal. Celtics coach Brad Stevens said Monday that he is not sure Thomas will be ready for the start of training camp.

Sources told ESPN that while Cleveland is not sure when Thomas will be able to return to the court, the Cavaliers have no short-term concerns about the injury. The team, sources said, is anxious to have its own doctors look at Thomas' hip and will spend the year monitoring it.

Thomas will become a free agent at the end of the 2017-18 season. He has said that he believes he's worthy of a maximum contract.

Isaiah Thomas, left, and Kyrie Irving were the last and first picks of the 2011 draft and now have been traded for each other. Brian Babineau/NBAE via Getty Images

Crowder, 27, has been a core piece of the Celtics' resurgence. A solid perimeter defender, the forward averaged 13.9 points and 5.8 rebounds last season. He also has one of the friendliest cap numbers in the NBA: $6.8 million, $7.3 million and $7.8 million the next three seasons. He does not become a free agent until the summer of 2020.

Zizic was the Celtics' first-round pick in 2016 (23rd overall). He's a highly regarded 20-year-old out of Croatia described by ESPN's Fran Fraschilla as "one of my favorite kids in this draft. He's 6-11, 240. He has a mean streak." In addition to his tremendous upside, Zizic was included for salary purposes.

Irving waived a $5.8 million trade kicker -- 15 percent of the total money remaining on his Cleveland deal -- to join Boston, sources said.

The trade will give Cleveland $29.1 million in tax savings. Cleveland's tax is now $49.3 million, down from $78.4 million.

The Celtics and Cavaliers open the season against each other Oct. 17 in Cleveland.

"Opening night should be interesting," a Cavs player who requested anonymity told ESPN.

ESPN's Chris Forsberg, Dave McMenamin and Bobby Marks contributed to this report.