Dallas Mavericks general manager Nico Harrison has defended the jaw-dropping trade that sent Luka Doncic to the Los Angeles Lakers in exchange for Anthony Davis, as a shell-shocked NBA struggled to comprehend the deal.

In a seismic development that sent shockwaves rippling throughout the basketball world, news broke late on Saturday that the Mavs are trading away Doncic – a 25-year-old five-time All-Star – in exchange for Lakers big man Davis as part of a three-team deal.

The extraordinary trade gives Dallas badly needed defensive heft with the acquisition of Davis, while the Lakers have at a stroke solved the riddle of how to prepare for life after LeBron James, the 40-year-old superstar who is the current face of the franchise.

Neither Davis, Doncic nor James were given advance warning that the deal was in the works, US media reported.

ESPN reported that James first learned of the deal while out for dinner in New York with his family following the Lakers' victory over the Knicks at Madison Square Garden.

In his first reaction to the move, Doncic took to social media to thank Dallas fans and looked forward to the next phase of his career.

"I thought I'd spend my career here and I wanted so badly to bring you a championship," Doncic wrote in a letter to Mavs fans.

James meanwhile saluted Davis's contribution to the Lakers in a caption over a photo of him embracing Davis on court. "Love you, my dog. Go crazy over there," James wrote, with a weeping emoji completing the post.

Dallas executive Harrison defended the decision to offload Doncic amid an outcry from the franchise's fans on social media, insisting Davis's arrival could turn the Mavs into title contenders.

"We think defence wins championships and we're bringing in one of the best two-way players in the league," Harrison said. "We're excited to feel like we're built to win now as well as in the future."

When asked if he could understand the frustration of fans at seeing a generational talent being traded away, Harrison said he believes such a move would help "make the organisation better".

In an inauspicious start to the post-Doncic era, the Mavs were blown out 144-101 by the NBA-leading Cleveland Cavaliers to fall to 26-24 on the season. (AFP)