It means there will not be the mouth-watering clash between Davies and Brian O'Driscoll - Gatland sticking with Scott Williams in the No.13 shirt.
Gatland did reveal however that Davies is set to turn out for the Scarlets against Treviso this weekend and with a rest week to follow Wales' clash with Ireland on Saturday, the head coach has pencilled in a return against France on February 21.
"He played for the Scarlets but still felt his chest a little bit," said Gatland.
"We just thought at the moment, with it being such a big game and midfield being such a competitive position it just feels like he needs more time and hopefully will be available then for France.
"Jonathan isn't quite right, he is training with us and will have another game next week."