Millwall have appointed David Tuttle as caretaker manager until the end of the season, with former boss Colin Lee becoming director of football.
Tuttle was previously Lee's assistant at the New Den
Tuttle becomes the club's fourth boss in a year, following Lee, Dennis Wise and Steve Claridge.
The 33-year-old, who has never managed a professional club before, will be the youngest manager in the Championship.
"We now have a long-term strategy which will enable us to build for success," said Millwall chairman Peter de Savary.
"Colin will oversee this process and have total responsibility for its implementation, in consultation with other members of the board.
"I have great confidence in Colin and I am convinced that, under his guidance, Millwall will move forward towards a very bright future."
MILLWALL'S UPS AND DOWNS
22 May 2004: Lions reach FA Cup final, losing 3-0 to Man Utd
8 August 2004: Chairman Theo Paphitis reveals plan to quit
7 February 2005: Lions say Jeff Burnige will replace Paphitis
8 May 2005: Manager Dennis Wise resigns
21 June 2005: Steve Claridge appointed boss
7 July 2005: Burnige resigns
27 July 2005: Colin Lee replaces Claridge
22 November 2005: Peter de Savary takes over as chairman
21 December 2005: David Tuttle appointed caretaker boss; Lee becomes director of football
The reshuffle follows a meeting between De Savary, chief executive Ken Brown, director Constantine Gonticas, Tuttle and Lee.
"It was a surprise, but the position excites me and I have a stack of work to do," said Lee.
"There is a clear understanding that David will keep the job for the rest of the season - and if he keeps Millwall in the Championship I'm sure he would keep the job.
"David is a young man, and the chairman wanted to give him a chance. I'm a perfectionist who finds it difficult to relax at certain times, whereas David is more laid-back.
"The players support the decision fully."
Tuttle's first match in charge of the first team will be the Boxing Day clash with Leicester.
Millwall are bottom of the Championship with 17 points from 20 matches.