Simon Easterby was not considered for selection due to an inflamed knee while Dwayne Peel (shoulder) and Alix Popham (hand) are also carrying knocks.
"I'm looking forward to playing alongside Nathan," said Evans. "When we played the Dragons a year or so ago he played at 12 that day and he proved quite effective. He offers lots of strength and we're both looking forward to the game."
Scarlets: Morgan Stoddart; Dafydd James, Gavin Evans, Nathan Brew, Matthew Watkins; Stephen Jones (Capt), Gavin Cattle; Iestyn Thomas, Matthew Rees, Deacon Manu, Vernon Cooper, Scott MacLeod, Dafydd Jones, Gavin Thomas, Nathan Thomas
Replacements: Phil John, Mahonri Schwalger, Lou Reed, James Bater, Liam Davies, Rhys Priestland, Darren Daniel