But Jones has made a swift recovery and is included in the squad for Scotland where Scarlets coach Nigel Davies is expecting a backlash.
Davies said: "It has been a pretty stern week reflecting on our performance in Edinburgh and we expect a far better one this week.
"When you lose a match one of the first things you look at is yourself - did you get selection right? did you get the preparation right?
"I spent a lot of time on the weekend looking at that and we have done things a bit differently this week.
"Maybe we took lots of things for granted, we accepted that players were doing things off their own back and maybe we were a bit light on them.
The Scarlets have a lengthy injury list with Kees Meeuws, Deacon Manu, Darren Daniel, Dafydd James, Simon Maling and Simon Easterby remain on the sidelines.
Scarlets - Ceiron Thomas, Mark Jones, Regan King, Gavin Evans, Morgan Stoddart, Stephen Jones (capt), Martin Roberts; Iestyn Thomas, Matthew Rees, Phil John, Lou Reed, Scott MacLeod, Dafydd Jones, David Lyons, Gavin Thomas.
Reps: Aled Hopkins, Ken Owens, Vernon Cooper, Nathan Thomas, Sililo Martens, Rob Higgitt, Jonathan Davies.