The Sky Bet Championship have confirmed their captain Jason Shackell is in talks with Derby after the two clubs agreed a fee and the bad news emanating from Turf Moor continued on Thursday.
Striker Gilchrist, 20, suffered the injury in a pre-season friendly with Rangers on Tuesday and has now learned he will need surgery to repair a fractured fibula.
“It’s a real shame for Jason,” boss Sean Dyche told the club’s official website.
“But he is good hands and he’ll have an operation in the next few days and be looked after well by our physio team.
“Naturally, he will be sidelined for a period of time, but we wish him well in his recovery.”
Gilchrist is yet to make his senior bow for Burnley but spent time on loan with Accrington last term.