Dwane Casey has guided the Toronto Raptors in their journey from the NBA hinterlands to the Eastern Conference final.

Now the Raptors are trusting Casey with the much tougher task of turning the Raptors into championship contenders.

The Raptors and Casey confirmed Tuesday that the two sides have agreed "on principal terms" of a three-year deal through the 2018-19 season. There was no confirmation of a dollar figure from the team but reports last week said the agreement was worth $18 million US.

It's a just reward for the coach who oversaw the team's most successful season in 2015-16, steering the Raptors to a franchise-record 56 wins in the regular season and a berth in the conference final.

"We're not there yet," Casey said at a press conference Tuesday, repeating one of his favourite mantras from last season. "There's work still to be done. Improvement from coaching to playing, all areas we can get better in."

Raptors GM Masai Ujiri promised last week that the deal would get done "in his sleep," and he worked quickly to make it happen.

Masai Ujiri, "Coach Casey has done a great job" 0:35

Casey was hired by former Raptors GM Bryan Colangelo after a 2010-11 season that saw the Raptors post a 22-60 record.

The Raptors missed the playoffs in his first two seasons, but he started moulding the team into a tough and defensively responsible unit. When Ujiri replaced Colangelo after the 2012-13 season, Casey survived the switch at the top and led the Raptors to three straight Atlantic Division titles.

Questions in free agency

"They key word is 'consistent,"' Casey said. "Guys know what to expect every day they come to work, they know the terminology, I know what Masai and his staff expect.

"I think each year two or three games are continuity wins for you. Guys are familiar with each other, they're where they should be in the defensive rotations, offensive rotations, just through continuity."

That continuity could be tested next season, as the Raptors will have key players DeMar DeRozan and Bismack Biyombo entering free agency next month.

DeRozan, a Raptor for his entire seven-year career, forms half of Toronto's dynamic backcourt along with fellow all-star Kyle Lowry. Congolese big man Biyombo came into his own during the playoffs, filling in admirably for injured starting centre Jonas Valanciunas. With DeRozan expecting to fetch a max contract and Biyombo in line for a huge raise, it's unlikely the Raptors can keep both players.