Foster stood down on Thursday night with his side currently bottom of the Ryman Development League North table with two points from their first nine games. Playing their home games at Holmesdale FC's Oakley Road Ground, the U21s are in action again next Monday night at home to Harlow Town.
Despite their lowly standing, six of Foster's players - Charlie Foster, Joel Massamba and Edgar Morais, Sean Law, Charlie Horbacki and Dillon Green - have made first team debuts or earned a place on the bench with Tony Russell's high-flying sides in Ryman South this season.
The Wands paid tribute to the work Foster has done in developing their younger players in a statement announcing his resignation and advertising for an experienced successor to come forward.
The club said: "All at Cray Wanderers would like to thank Phil for his sterling work in getting the U21 team up and running and the dedication shown to getting a team in the Ryman Development League North.
"Phil has worked tirelessly for Cray Wanderers from youth level and helped keep many of his Kent Youth League U18s side with the club in preparation of the move to the tough competition of the Ryman Development League. We wish Phil well with his future endeavours in the game."
For more information, potential candidates should call 07973 498493.
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