"We always had the intention of trying to get Simon through these two games when he came back from Ireland duty," said Davies.
"However, the minor problem has flared up again after Saturday's game so it's important he gets the knee seen to this week. Saying that, we've still got 17 internationals in the side to play Toulouse, including three British Lions, and Dafydd Jones is raring to go in place of Simon."
Jones will make his first start in Europe this season on the side of the scrum while Vernon Cooper makes way for Adam Jones in the second row.
In the front row Craig Dunlea comes in for fellow Kiwi Deacon Manu who moves to the bench, while there are two changes in the backs. Darren Daniel takes over on the wing from Mark Jones who also has a slight knee strain while Barry Davies replaces Ceiron Thomas at fullback.
Davies added that Matthew Watkins, Phil John, James Bater and Aled Gravelle weren't considered because they are still recovering from injury.
Scarlets: Barry Davies, Dafydd James, Regan King, Gavin Evans, Darren Daniel, Stephen Jones, Dwayne Peel (capt), Iestyn Thomas, Matthew Rees, Craig Dunlea, Adam Jones, Scott MacLeod, Dafydd Jones, Gavin Thomas, Alix Popham
Replacements: Ken Owens, Deacon Manu, Inoke Afeaki, Nathan Thomas, Liam Davies, Ceiron Thomas, Garan Evans
Referee: Chris White (England)