Assistant boss Danny Orr will leave Castleford Tigers at the end of the 2020 season to seek new opportunities in his coaching career.
The 42-year-old had two stints as a player at his hometown club in a 15-year spell and was a Great Britain-capped international half-back.
He then moved onto the coaching staff under Ian Millward, and was retained under successor Daryl Powell.
"It's been a very tough decision to make," Orr said.
"But [it's] one I feel that I have to do at this stage of my coaching career. I would like to thank everyone at the club for the support I've received over the years and to wish Powelly and the boys all the best for 2021."
Orr, along with fellow assistant Ryan Sheridan and Powell, helped create a style of rugby league which caught the eye and helped Castleford to a Challenge Cup final in 2014 and a Grand Final in 2017.
The team also brought the best out of Luke Gale, helping the scrum-half to earn England honours and play in the 2017 World Cup final.
"Danny has been a phenomenal servant for Castleford Tigers as a player and as a coach and has been a massive support to me over the last seven years in my time at the club," Powell said.
"Danny will be with us for the remainder of this season and I know he will continue to help drive our standards of performance.
"I respect his decision to want to advance his coaching career as we move into 2021 and I wish him all the best."