Hewitt, who last week made his 100th appearance for the region, is named at inside centre as Cory Allen switches to outside centre for the Pool 2 opener in Devon.
Director of Rugby Phil Davies makes no further changes to the side that defeated Edinburgh Rugby last time out, with hooker Matthew Rees again captaining from the front row and making his 50th appearance in the Heineken Cup.
Fellow hooker Marc Breeze is named among the replacements and there is also a call-up for Richard Smith who could make his first appearance of the season from the bench.
Blues have won three of their last four Heineken Cup encounters with clubs across the Anglo-Welsh border.
However, Davies is aware of the size of the challenge facing his Blues against an Exeter side that warmed up for Europe with a convincing win over Gloucester last weekend.
“We know the physical battle we will face and we have got to be ready to match that,” he said.
“We’re trying to get intensity into our game. I know what the English league is like and how pragmatic it can be. Exeter have been that, but they have also tried to open their game up and play more expansively and they are an exciting side.
“It’s eight versus eight up front and a real battle. But there are battles all over the pitch in terms of physicality, speed and power. The word intensity in the player’s minds has got to be the forefront this weekend.
“This competition is all about momentum. All the Welsh regions have got match winners and players with proven ability. If we get momentum who know what can happen this season?”
Blues will be missing Owen Williams, who is ruled out after suffering a hamstring injury last week against Edinburgh, but Davies is confident a new-look midfield partnership of Dafydd Hewitt and Cory Allen can shine.
“We are lucky that Cory has had some really good game experience over the last few weeks and Dafydd has been there, seen it and done it all before. We have two guys there that will do a very good job for us.”
