"I haven't thought about what I'm going to say to the players yet, or how to refer to the Scarlets. I spent a long time playing for them and still have a lot of good friends there," admitted Rees.
"I'm sure something will come to mind at the time and there certainly won't be any thought of taking it easy on old friends. This is a game we want and need to win."
It will Rees' first start since recovering from cancer and the 58 times caped hooker knows he is in for a tough challenge against his former Welsh rival Ken Owens in the front row battle. The Blues have been resurgent since their captain's return, edging out Ulster at the Arms Park before claiming a hard-fought away victory against an in-form Edinburgh.
Rees is one of three changes to the starting line-up for the Blues as they aim to make it three successive league wins. Centre Dafydd Hewitt is also called up after his late try against Edinburgh last week and Wales lock Bradley Davies returns to action for what will be his first start of the calendar year after coming on as a replacement in the Scottish capital.
Wing Chris Czekaj, who heads to Colomiers in the summer, will hit another memorable milestone in his career as he plays his 100th game in the RaboDirect PRO12. Hooker Rhys Williams and lock Chris Dicomidis are named among the replacements
The Scarlets are chasing a ninth successive win over the Blues, and a fourth straight PRO12 triumph,
and welcome back John Barclay, Samson Lee, Phil John and Gareth Davies for the clash. They all missed last weekend's home win over Zebre.
Gareth Maule also makes a return to the starting line-up alongside captain Jonathan Davies, while Ken Owens also makes a return to the front row. Back row man Josh Turnbull, who will be joining the Blues next season, moves to No 8 with Sione Timani moving to the replacements bench.
The Scarlets are still looking to lock down ing the magical sixth place that will bag them a place at the top table of European rugby next season in the new format. They have lost their three Welsh derbies to date this season and Rhys Priestland knows a win is the bare minimum that is required today.
"A few teams are creeping up behind us, so now we just have to aim to finish in the to six and a win on Sunday would go a long way towards getting that spot," said Priestland..
"My personal opinion is that we blew our chances of a play-off spot over the Christmas period. We lost to the Ospreys twice and then to Munster away. I think that was the point where we shot ourselves in the foot."