Rees was Wales captain during the 2011 RBS 6 Nations but was forced to give up the armband for the World Cup after undergoing neck surgery in August that ruled him out of the tournament.
The 30-year-old has been named on the bench while fellow Welsh internationals scrum-half Tavis Knoyle and centre Scott Williams are also among the replacements.
And Davies revealed his relief in the rapid progress made by the hooker.
"Matthew is fit and ready to go," Davies said. "He has been a big influence and it is great to have someone of his rugby ability but also his influence back.
"We weren't quite sure when he went for the operation how long the recovery would be, but it has been good news, we are delighted.
"He is happy and pain free as well, it is great news for us.
"With regards to the others [internationals], it will be based on game time with Wales, the other players will be back a week Thursday, a couple of days before the Ospreys game.
"I have spoken to the players and it is up to them. If they are keen to play and feel up to it, then great."
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