Carsley, 22, helped fire Brig to promotion last season after joining from Longridge Town, and only signed a new deal back in August.
Director of football, Neil Crowe, said: "We received a request from Brad for him to be released from his contract and we [the club] have today reluctantly agreed to the request.
"We'd like to thank Brad for his service to the club and wish him all the best for the future."
Carsley later tweeted: "I’ve made the decision to leave the club, just like to say thank you to everyone involved at the club for the last two years and thanks for some great memories, all the best for the rest of the season."
There has been no news as yet as to what his future holds.
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