"Ricardo landed very heavily on his left knee at Coventry. The knee unfortunately started to swell up very rapidly," physio Andrew Balderston told the club's official website.
"He had an MRI scan on Monday at Lytham and this showed he has no significant ligament damage at all, so structurally the knee is intact.
"We still had a little bit of concern because we don't know where exactly the blood is coming from, so on Wednesday he will have a small operation at Fulwood to get a better prognosis."
Fuller is now definitely out of the Worthington cup tie at Aston Villa on Wednesday and also this weekend's clash with Wimbledon.
"We were hoping to have Ricardo back for Saturday, but that will obviously not be the case. He'll have the blood removed with an injection and then the op tomorrow and it looks like a week on Saturday at least," said manager Craig Brown.
"With Richard Cresswell suspended for Saturday it gives David Healy and Pawel Abbott, who has been performing extremely well in the reserves and in training, a great chance to shine."