The 29 year old left Kilmarnock on a free transfer after scoring 16 times in 18 months for the club.
“The mesh which keeps it (the knee) reinforced came away a wee bit so he needs a small operation to tighten that up,” Jefferies told the club’s official website.
“They thought they would get away with an injection so we’re back to what we should have maybe done at the start.
“It’s probably a two or three-week thing, so he might miss the start of the season.
“He’ll be a miss for the start of the season but you never know.
“Even if I could get him handy for the bench if I needed him to come on, if he could not manage 90 minutes.”