Kerry Hardwell has taken the decision to step down as Rustington boss.
In his first season in senior management, he guided the Blues to double glory.
Rustington were crowned Southern Combination League Division 2 champions - losing just once on the way to the title - and they lifted the League Cup.
However, Hardwell has announced the shock decision to leave the club.
The departing boss revealed his sole season in charge will be an experience he will 'cherish forever'.
But Rustington are now searching for a third manager in as many season after he walked away from his role.
Hardwell confirmed his departure in a social media post.
He said: "After much thought I have decided to step down as first team manager for next season at Rustington FC.
"I've had the best season winning the league and league cup and it's an experience I will cherish for the rest of my life.
"As I think you've all gathered, I've really enjoyed every single minute of my time with Rustington.
"It literally is the best club, with some fantastic people involved.
"A big thank you to Mark, Ash and Tucks for believing in me this season and all the players for their fantastic attitudes and hard work.
"CHAMPIONS. Up the Ton."