The hooker, who has 58 caps for Wales and three for the British and Irish Lions, will take on his former side in the first Judgement Day battle at the Millennium Stadium this Sunday.
The Cardiff region have made two further changes. Wasps bound lock Bradley Davies and Dafydd Hewitt, their match-winner against Edinburgh come into the starting line-up.
Rees played nine seasons for the West Wales region and will now face them for the first time since his emotional return from cancer.
The Blues have been resurgent since their captain’s return, edging out Ulster at the Cardiff Arms Park before claiming a hard-fought away victory against an in-form Edinburgh.
Blues interim Head Coach Dale McIntosh hailed Rees’ influence since returning from the illness.
He said: “The senior players coming back in has helped us; the likes of Gethin Jenkins, Matthew Rees, Alex Cuthbert, I think we have turned ‘a’ corner but not ‘the’ corner with recent results. We’ve improved and we’ve won two games, but it’s only two games.
“We face a formidable challenge on Sunday and perhaps we will see where we really are. It’s only two games we have won and we need to keep building.
“We want passion and desire from our players. We will need that tenacity and edge. That promotes accountability, firstly in training and secondly in the game. We don’t players to drift through the week because what you do in training you take into the game.
“The senior players get out there and make the youngsters understand that is not acceptable. Accountability comes on the pitch when the guys are next to you on the battlefield. When he is shouting at you that is when you have to stand up and take notice.”
