The 19-year-old had enjoyed a run at right-back before he was ruled out of last weekend's 1-0 victory at Walsall. An assessment has shown he needs a period of rest.
"It's obviously disappointing for Jordan because he has come in for Cyrus and acquitted himself extremely well, so we hope he makes a speedy recovery," boss Steven Pressley told the club's official website.
Aaron Phillips replaced Willis in the starting line-up and Pressley is confident he will prove to be a more than able deputy.
"Aaron Phillips has impressed though when he has made appearances, so while news of injuries is always disappointing, it's been encouraging to see our young boys stepping up to the mark," Pressley added.