Carlisle defender Frank Simek faces an extended spell on the sidelines after tearing a calf muscle.
The American full-back had only recently returned to full training following his recovery from a torn thigh muscle sustained against Notts County on the opening day of the season.
Manager Greg Abbott told the club's official website: "Frank has been really unlucky and I'm sure he'll be very frustrated. However, the important thing for him and us is that we get him back to full fitness as quickly as possible. He'll be looked after on a day-by-day basis to make sure that he comes back ready to go."
Simek, 27, joined the Cumbrians on a free transfer from Sheffield Wednesday in the summer of 2010 and was a virtual ever-present in the side last season.