In a surprising move, a league source said the Bulls will not renew the contract of lead assistant coach Ron Adams, whose deal expires Sunday.

Adams, in his second stint with the Bulls, returned in 2010 after a successful run as Scott Brooks’ lead assistant in Oklahoma City. Adams left the Thunder in part to join longtime friend Tom Thibodeau’s first staff and also to live again with his family. It had remained in the Chicago area for school reasons following Adams’ first stint with the Bulls under Scott Skiles.

According to sources, general manager Gar Forman made the decision, not Thibodeau. Forman informed Adams on Friday.

Reached Saturday, Forman said the team doesn’t comment on personnel matters. Adams also declined comment. A call to Thibodeau wasn’t returned.

The move raised eyebrows within and outside the organization as perhaps the first public indication of tension between Forman and Thibodeau. Though management has final say, head coaches typically are in charge of their staffs and the Bulls have made three straight playoff appearances. Thibodeau, for instance, let go Pete Myers when he first took over, a longtime franchise fixture.

Adams, who had been working on one-year deals since leaving the Thunder, consistently ranked among leaders in voting for the league’s top assistants on the annual general managers’ poll the NBA releases. Players praised Adams for his developmental work, particularly in improving form and release points on jump shots.