Butler, who had only just returned from a hamstring injury that kept him sidelined for four months, was forced to withdraw from the Republic of Ireland Under-21 squad for last week's game against Georgia with this latest setback in a season which as seen him play just seven first team games.
"This season has been a nightmare for me," he told the club's official website.
"I want to get fit as quickly as possible and am looking forward to starting afresh."
