Wakefield head coach Richard Agar has quit his job with immediate effect and has been replaced by his assistant James Webster, the Wildcats have announced.
Agar, who was in his post for two-and-a-half years, stepped down in the wake of his club's 20-12 defeat to First Utility Super League relegation rivals Bradford on Sunday.
Wakefield c hairman Michael Carter said: "I'd like to thank Richard for all he has done for this club.
"Reaching the play-offs in 2012 given where the club was when he arrived was a remarkable achievement and gave the fans some terrific memories."
Agar, who was in charge of Hull for four seasons from 2008, succeeded John Kear at Wakefield in October 2011 and defied expectations by guiding them to a play-off spot in his first campaign on the back of a club Super League record run of seven successive wins.
He achieved that improbable success despite being forced to bring in 20 new faces and was faced with a similar task at the end of last season when financial difficulties forced the club to shed several high-profile players. The Wildcats have won just four of their 15 matches so far.
Agar, who was coach of France at the 2013 World Cup, said: "I spoke with the board of directors a number of weeks ago outlining the reasons why I had decided to look for another job within the game at the end of the season and therefore requested a release from the remaining two years of my contract.
"All parties felt that with a new coach being decided upon and the club entering the recruitment period, it would be hard to continue in the role, especially with the players knowing I was going. It would also allow James to start putting into place his plans for next season.
"The club has recently faced some extremely difficult and uncertain times and hopefully will be in a position in the near future to provide stability and consolidate their position in the top flight and give James the resources he needs to be successful.
"The club has a tremendous spirit about it and I would like to take this opportunity to wish Michael and Chris (Brereton) all the very best for their future ownership of the club."
Carter added: "Richard Agar is an outstanding person and I wish him every success in his future career.
"He has put together a group of players which we are fully confident has the quality to achieve our main objective of survival in the First Utility Super League.
"Throughout all of the tribulations the club has endured during his tenure he has handled himself with superb dignity and worked tirelessly for the cause. We fully respect his decision to move on and all parties were in agreement that the timing was right for James Webster to take charge."
Webster, a 34-year-old Australian who worked alongside Agar at Hull as well as Wakefield, takes charge straight away and his first game will be against bottom club London Broncos at the Rapid Solicitors Stadium on Friday week.
"I would like to thank Michael and the board for giving me the opportunity to coach Wakefield Trinity, a club steeped in tradition," said Webster, who played for Hull KR and Widnes.
"Everyone at the club knew this would be a difficult year with some hurdles to overcome, but we've set some goals and if we are successful in reaching them then I believe the club will be in a much stronger position going forward.
"Rich has to be credited for rebuilding this team through some adverse times. I would personally like to thank him for the time he has invested in me and wish him all the best."