Milligan's bad break
Milligan suffered the injury last week after recently breaking back into the first team.
The 22-year-old had scored in his two appearances prior to his injury but is devastated to be sidelined.
The former Everton man is out-of-contract at the end of the campaign and fears the injury could jeopardise his prospects of clinching a fresh deal.
"I'm absolutely gutted," Milligan told the club's official website.
"It's hard because it's the first real injury I've had. I'm on crutches at the moment.
"Hopefully, I should be able to start putting weight on it in a few weeks but it will probably be two to three months before I'm playing again.
"It's a nightmare because my contract is up at the end of the season and new deals are usually sorted out by December.
"I'd been working hard in training and had just started to get back into the team.
"I felt I was starting to play some good football and to have this happen is a massive blow."