Halfpenny and Powell get first starts
Halfpenny, 19, replaces injured Scarlets wing Mark Jones, while number eight Powell packs down in the back row alongside his Blues colleague Martyn Williams and skipper Ryan Jones.
Ospreys hooker Huw Bennett, who was injured on EDF Energy Cup duty two days ago, is another absentee, with Scarlets’ Matthew Rees starting in the number two shirt.