The teams apparently sought to complete the deal Thursday before midnight to ensure its completion, with a lockout expected at 12:01 a.m. ET Friday.
The Cavaliers have been shopping Hickson for some time and have decided to part with the young power forward in exchange for Casspi, who has been coveted for his combination of defense, energy and underrated perimeter shooting by numerous teams after two solid seasons with the Kings.
"We like Casspi," said Cavs general manager Chris Grant, who wouldn't say if he expects Casspi to start immediately. "He's a tough, athletic, 6-foot-9 kid. He's got a nastiness and fight about him."
Casspi, who said in a teleconference from Los Angeles that he was excited about coming to Cleveland to play for coach Byron Scott, wondered what Grant meant about him being "nasty."
"Sometimes I play hard," he said with a laugh, "and sometimes I might play too hard."
Grant was quick to point out that Casspi, who played two seasons with the Kings, made 47 percent of his 3-point tries from the corner, another weapon for Scott and a target for Irving.
"It gives us a chance to give the guys room to grow on the court together and gives our roster more balance financially moving forward," Grant said. "I felt that, where our team is, and where it's headed, that this was the right move for our franchise."
The deal, though, also illustrates the decline in Hickson's stature within the Cavaliers' organization. As recently as the 2010 trade deadline, Cleveland's talks with Phoenix on a trade for Amare Stoudemire stalled in part because of the Cavs' reported reluctance to include Hickson in the deal -- although sources with knowledge of those talks insisted Thursday that the Cavs were prepared to go through with the deal and that the Suns were the team that backed away.
Hickson, 22, became a focal point of Cleveland's offense last season after the free-agent defection of LeBron James, but he clashed at times with Cavs coach Byron Scott despite averaging 13.8 points and 8.7 rebounds in 28.2 minutes per game.
"I'm kind of glad it's over with so my name is not involved in so many trade rumors," Hickson said. "I think the Kings did a good job in picking up a young athletic big that is going to give his all and give it 110 percent."
Sources say Sacramento, meanwhile, thinks it can make room for Hickson by shifting prized second-year forward DeMarcus Cousins to center on occasion. The Kings also still have Jason Thompson as another trade asset with Cousins and Hickson ahead of him.
"This is a chance to acquire a young player that has already proven himself to a pretty decent level in the league and someone who can strengthen our roster," Kings GM Geoff Petrie said. "There is still a lot of upside there. A lot of the players taken in the draft a week ago are not that much younger than J.J. and he has had three years in the league and he was getting more productive each year."
Kings coach Paul Westphal is excited about the Hickson-Cousins-Thompson trio.
"He is a really good fit," Westphal said. "All three of those players can play a little bit (of) center and power forward. It gives us a very solid rotation. (Hickson) has shown versatility and ability to fit in. I don't think that you necessarily have to run every play for him to have him be effective. But at the same time, he can be effective if you run plays for him.
"He's somebody that we are getting at a real good time in his career. He's already shown a track record of success."
Marc Stein is a senior NBA writer for ESPN.com. Information from The Associated Press was used in this report.