The Welsh number 10 endured a difficult autumn series but Wilson is under no illusions as to how important he is to the region.
"Class is permanent - and as far as I'm concerned that's true of Rhys," he said.
"It's excellent to have him back with us. He will breed confidence within the backs division and to have a player of his calibre, talent and intelligence on the field will be key in this game.
"He is a real pro and even if he's not been at the top of his game at times, he certainly has the ability and commitment to come back.
"There's no doubting what he does for the Scarlets, his commitment to this region and his involvement on the field is central to our success."
Alongside Priestland, Wilson and head coach Simon Easterby are able to name a hugely strong side featuring a number of returning internationals.
Jonathan Davies, Scott Williams, Liam Williams, Matthew Rees and Aaron Shingler all start as the Scarlets look for their first win in the competition so far this season.
George North though, is still unavailable.
Davies captains the side alongside centre partner Williams while young Carmarthen scrum half Aled Davies gets a huge opportunity with his first European start.
With Priestland controlling things at fly-half, Dan Newton at starts at full-back with Liam Williams and Andy Fenby on the wings.
While a number of fringe players having impressed for the region during the autumn internationals, Wilson has welcomed the return of his star men, albeit after a short turnaround.
"We knew from the outset how tight it would be for us bringing back the internationals as we go into these double headers in Europe," he added.
"Of course it's difficult with just a week's prep and with the intensity of international rugby and how that impacts the players' bodies.
"But you just get on with it. It's another challenge you face and all that really matters is getting a result on Saturday and for our players returning it's another intense game of rugby."
The Scarlets take on an Exeter side who have impressed in their debut season in the Heineken Cup.
"Credit to Rob Baxter, his coaching staff and the players for what they have done over the last three years from Championship to Premiership rugby and qualifying for Europe for the first time," said Wilson.
"They have developed well and become a very strong side and can use both brands of rugby now, not just the forward dominated game of scrum, driving line-out and a heavy carrying game that they are renowned for.
"They've started trying to play with width and run from deep and had some success.
"We are not under any allusions how good they are and come here on the back of some impressive form."