The Oklahoma City Thunder are promoting assistant Mark Daigneault to become the franchise's next head coach, sources told ESPN on Wednesday.

Daigneault's elevation to replace the departed Billy Donovan completes a rapid six-year rise within the franchise, which included a five-year run as the OKC Blue's G League coach, where Daigneault had a .572 winning percentage and three division titles.

Daigneault, 35, takes over the Thunder within three weeks of the opening of training camp on Dec. 1, with a roster that could well be in flux between now and opening night on Dec. 22.

Thunder executive vice president and general manager Sam Presti is showing faith in Daigneault's skill set to transition from what could still be a Western Conference playoff contender in 2020-2021 to something resembling more of a rebuild around key young players such as Shai Gilgeous-Alexander, Lu Dort and Darius Bazley. The Thunder are fortified with a possibility of 15 first-round picks and four sets of pick swaps between the 2020 and 2026 NBA drafts.

Daigneault moved to the Thunder's coaching staff for the 2019-2020 season, joining Donovan on the front of the bench in a season when the Thunder earned the sixth seed in the Western Conference playoffs. Donovan's contract expired, which eventually led him to accept the Chicago Bulls' head-coaching job. Daigneault was part of a weekslong search that included candidates meeting a number of times with Thunder officials.

Presti has been enthusiastic over Daigneault's proven track record in the Thunder organization, sources said, including connecting with players, teaching the game and making the kind of short- and longer-term adjustments that are crucial for a franchise that is transitioning out of playoff contention and toward a younger, developmental roster. In his time as a G League coach, he was 143-107 with four playoff appearances and eight players called up to NBA rosters, including four players signed to two-way deals, in the past season.

Presti hired Daigneault out of the University of Florida in 2014 -- a year before he lured Donovan from the Gators to become the Thunder's head coach. Daigneault had been an assistant at Florida and the College of the Holy Cross. He graduated from the University of Connecticut in 2007, where he had been a student manager under Hall of Fame coach Jim Calhoun.

ESPN NBA reporter Royce Young contributed to this report.