Lions assistant coach Beau McDonald told NIRS Radio that Power sustained the injury last night and did not recover.
Claye Beams has been brought into the 22.
"Lukey’s hurt his back last night and didn't pull up well enough this morning," McDonald said.
"Beamsy offers as much run as Luke so we decided to bring him straight in (and leave Amon Buchanan as the sub)."
Power joins Josh Drummond and Matt Maguire on the sidelines for the Lions.
