The 29-year-old has been ruled out for up to four months after sustaining a torn hamstring tendon injury.
Devitt, who has made two appearances for Bradford since joining the club on loan, suffered the injury in the EFL Trophy game against Bolton Wanderers.
The Irishman is to undergo surgery on the injury this weekend.
Bantams boss and former Blackpool manager Gary Bowyer said: "It is a massive blow for Jamie and for us as a club. It is frustrating with the innocuous way in which he sustained the injury.
"He has settled in very well and we are going to fully support him for however long he will be missing.
"We all know injuries are part and parcel of football. It is our job and his job to rediscover the form he showed before his injury, once he returns."