The Pistons are expected to offer Frank a contract this week.
The 70-year-old Brown has 1,098 wins in 2,002 career games as a head coach for the Denver Nuggets (1976-79), New Jersey Nets (1981-83), San Antonio Spurs (1988-91), Los Angeles Clippers (1991-93), Indiana Pacers (1993-97), Philadelphia 76ers (1997-2003), Detroit Pistons (2003-05), New York Knicks (2005-06) and Charlotte Bobcats, where he went 88-104 in 2+ seasons before resigning on December 22, 2010.
Brown led the Pistons to an NBA Championship in the 2003-04 season.
According to Wojnarowski, Rivers is expected to promote current assistant Mike Longabardi, but Brown and Rivers are close friends, with Brown previously expressing an interest in joining the Celtics' coaching in staff in 2007. A source close to Brown tells Yahoo! that Brown is willing to work for "less than the going rate".
For more on the Celtics, visit CelticsBlog.