Begley added that the Knicks are expected to hire Keith Smart—who served under Fizdale with the Memphis Grizzlies—as a top assistant as well.
Per Begley, Knicks general manager Scott Perry was part of Detroit's front office when Sullivan was with the Pistons.
He has spent the past two seasons on the Los Angeles Clippers staff under head coach Doc Rivers and previously held positions with the Detroit Pistons, New Jersey Nets and Washington Wizards.
Prior to his NBA coaching career, Sullivan was a part of three Final Four appearances as an assistant coach at alma mater North Carolina, where he had previously reached the Final Four three times as a player.
Buechler has spent the past two seasons as an assistant under Luke Walton with the Los Angeles Lakers.
Prior to that, he spent 12 seasons in the NBA as a player with the Nets, San Antonio Spurs, Golden State Warriors, Chicago Bulls, Pistons, Phoenix Suns and Orlando Magic.
Buechler won three NBA championships as a reserve with the Bulls.
The Knicks are building a new staff under Fizdale, who was announced as the team's new head coach May 7 after the firing of previous head coach Jeff Hornacek.
Fizdale led the Grizzlies to one playoff appearance across two seasons as Memphis' head coach, and he will look to take the Knicks back to the postseason for the first time since 2012-13.