Davies is also without locks Vernon Cooper, Simon Maling, Lou Reed and the suspended Scott MacLeod with Wales flanker Dafydd Jones filling in as an emergency alongside Dominic Day.
Davies said: "Dominic has had an opportunity to show what he can do and we have been delighted with him"
With Wales' Invesco perpetual Series opener against the Springboks eight days away, Stephen Jones, Matthew Rees and Martin Roberts start on the bench as the Scarlets bid to reach the semi-finals.
The Scarlets lie three points ahead of Northampton and four ahead of Saracens but face a Guinness Premiership side defending a 20-game unbeaten record at home in all competitions.
Scarlets: Morgan Stoddart; Rob Higgitt, Regan King, Gavin Evans, Matthew Jacobs; Ceiron Thomas, Sililo Martens; Iestyn Thomas, Ken Owens, Kees Meeuws, Dominic Day, Dafydd Jones, Nathan Thomas, Simon Easterby (capt), David Lyons. Replacements: Phil John, Matthew Rees, Josh Turnbull, Gavin Thomas, Martin Roberts, Stephen Jones, Jonathan Davies.