The other two changes come in the pack as loosehead prop Gethin Jenkins makes his first league appearance for the region since returning from France this summer and will he pack down with Matthew Rees and Taufa'ao Filise in the front row.
Lock Bradley Davies is also recalled to the starting line-up after serving a suspension and will team up with Filo Paulo in the second row.
Flanker Josh Navidi will make his 50th appearance for the region in the back row alongside Sam Warburton and Andries Pretorius.
There is also a potential major milestone for centre Dafydd Hewitt who is named among the replacements. If Hewitt comes off the bench he will make his 100th appearance and become a centurion for Blues.
Davies said: "Our challenge is to continue to improve and build on what we produced last week against Leinster.
"We played with real pride and emotion in Dublin and for long periods of the game more than matched the defending champions.
"It was a display full of fire and fight and showed we have got some steel about us. Now we've got to produce that same level of performance in front of our own supporters.
"There are still things that we need to work on, but what we are pleased about is that we are continuing to create opportunities," he added.
"We've scored some great tries in recent games and in Ireland could have scored a few more if we had been more clinical.
"We have just got to be more efficient in what we do and once we start doing that we know we will get the results we want."
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Cardiff Blues: 15 Leigh Halfpenny, 14 Alex Cuthbert, 13 Owen Williams, 12 Cory Allen, 11 Harry Robinson, 10 Rhys Patchell, 9 Lloyd Williams; 1 Gethin Jenkins, 2 Matthew Rees (c), 3 Taufa'ao Filise, 4 Bradley Davies, 5 Filo Paulo, 6 Josh Navidi, 7 Sam Warburton, 8 Andries Pretorius
Replacements: 16 Kristian Dacey, 17 Scott Andrews, 18 Sam Hobbs, 19 Lou Reed, 20 Robin Copeland, 21 Lewis Jones, 22 Gareth Davies, 23 Dafydd Hewitt