Manager Kevin Dillon confirmed the news after a scan that was undertaken with Physiotherapist Nick Brink as the first team squad continue their pre season training schedule in Somerset at Millfield School.
Speaking to The Shots Online he said, "It is disappointing news for Jack and for the whole squad too. Jack had been doing really well since his arrival from Crystal Palace and had perfomed well in the match up to that point too."
"He was caught with his standing foot and it all looked something of nothing at the time but we have had confirmation that it is a fractured bone in his ankle and Jack will be in plaster for the next six weeks or so.
"He is likely to be out of action for up to three months which is a set back especially considering that it is his first bad injury. On the positive side he will come back fitter and stronger due to the rehabilitation plans and programmes that we now have.
The boss has also confirmed that he is still aiming to bring in another striker prior to the start of the campaign.