Nineteen-year-old Davies, who was recently named in the Wales U20 squad for the Six Nations, comes in for Martin Roberts who drops out of the squad completely.
North Walian back row Rob McCusker (24) starts at flanker for the Dragons game, having put in a strong and physical performance in the second half against the Ospreys on Boxing Day.
McCusker replaces Simon Easterby who sustained a hand injury during the sell-out Boxing Day derby at Parc y Scarlets. Easterby has fractured a finger and will be out for around five weeks.
Centre Rob Higgitt and flanker Richie Pugh return to the Scarlets 22, Pugh now fit following a shoulder injury picked up against Leinster in the Heineken Cup.
Lee Williams comes in on the wing to replace Morgan Stoddart who picked up a minor groin injury against the Ospreys last weekend.
The Scarlets go into Welsh derby having won their three last games against the Dragons, and have been victorious on four of their last five visits to Rodney Parade.
However, Scarlets Head Coach Nigel Davies knows that based on the Dragons’ 100% home record in the Magners League this season, his young Scarlets team will be facing a tough encounter.
He said: “It’s another big game for us, the Dragons are playing a very expansive brand of rugby and getting on the right side of results.
“They have had an excellent home record in the Magners this season, it will be tough to go there – particularly as we’re carrying a small squad at the moment with eight of our front-liners now out through injury.”
Scarlets Captain David Lyons said there was plenty of spirit shown by his team against the Ospreys on Boxing Day and that the Dragons game would have the same level of intensity.
“It will be a similar sort of game to the Ospreys, a good atmosphere at Rodney Parade and probably a big crowd – we’ll have to work hard but we also know we have enough skill and talent to get the result, we just need to keep our focus and play for the full 80 minutes.”
Scarlets: 15 Rhys Priestland, 14 Lee Williams, 13 Sean Lamont, 12 Jonathan Davies, 11 Andy Fenby, 10 Stephen Jones, 9 Gareth Davies, 1 Phil John, 2 Ken Owens, 3 Deacon Manu, 4 Lou Reed, 5 Dominic Day, 6 Rob McCusker, 7 Johnathan Edwards, 8 David Lyons (captain).
Replacements: 16 Jamie Corsi, 17 Emyr Phillips, 18 Damian Welch, 19 Richie Pugh, 20 Daniel Evans, 21 Gareth Maule, 22 Rob Higgitt.
