The Vanarama National League North club yesterday announced that their only ever manager is to leave the club.
Karl Marginson, in charge of the Red Rebels since formation in 2005, is now out of work with United struggling for form.
Fans’ favourite Greaves has been asked to step in and has said today he needs the fans’ full backing to help the club through a difficult period.
“It has been a strange 24 hours and an unexpected one at that,” said the striker, who joined the club in 2012.
“I was as surprised and gutted as anyone at Margy’s departure as he has been unbelievable for the five years I’ve been at the club. I owe the man everything for my opportunity to play here for so long.
“It’s a sad time for the club as I know first hand how much they all loved this club and want it to succeed on and off the pitch.”
Greaves added: “I have been asked to take temporary charge and I’m massively honoured even to be considered for this role.
“I can assure everyone at FC United - fans, players and staff - that I will give it everything I’ve got for however long it may be both on and off the pitch.
“All I ask is everyone continues to get behind the lads and be the famous twelfth man that we are renowned for.”