They're both included in the starting line-up for the pro-squad's first game at Parc y Scarlets - against European champions Munster and in front of a live TV audience.
However, both 20-year-old Davies and 21-year-old Priestland are comfortable with the Parc's Magners League experience and have already made their mark at the £23m stadium which has replaced the 129-year-old Stradey Park.
The first Parc y Scarlets game, on November 15, saw them star in the Principality Premiership as Llanelli RFC beat Cardiff RFC 32-3.
Priestland scored the first points, with a first-half penalty goal, Davies bagged the first try with a typically muscular effort from centre in the second half.
Against Munster, Priestland starts at 10, Davies at 11. Other young talent on board includes hooker Ken Owens, age 21, and second row Dominic Day, 23. The bench features promising backrows Rob McCusker, age 23, and Johnathan Edwards, 24.
Davies said: "It's always special to score a try but the one against Cardiff came on a big occasion so it's one I'll always remember. I was really proud to score that try. Before we ran out against Cardiff, some of the boys talked about who'd score the first try but the really important thing was just to get the win."
Davies played junior rugby at St Clears before moving on to Whitland Youth and joining the Scarlets Academy in his mid-teens. He's convinced that the move to Parc y Scarlets will encourage even more dynamic young talent to come through the ranks.
He said: "The facilities here are brilliant - it's a top place to develop young players so I'm sure it's something even more young players will aspire to. If I was a kid now, I'd certainly want to be out on the Parc y Scarlets pitch, playing and scoring tries."
Scarlets head coach Nigel Davies told a Parc y Scarlets press conference yesterday: "The Munster game is a big occasion as much as anything else. Arguably the final game at Stradey was the biggest game of our season, now you could argue that we've got an even bigger one.
"It's very important that we make visitors realise that this is our home so we must start strongly here and start making the place our.
"Munster are bringing a pretty much full-strength squad and that's great because they have an unprecedented pedigree in the professional game and it'll be a real test for us. They bring an intensity that's second to none and that has really helped to focus our minds.
"Injuries mean that, although we're strong up front for the Munster game, we're a little low on numbers behind the scrum, with a couple of long-term absentees, a few short-term injuries and a couple of guys away with Wales.
"We're very focused indeed on giving our supporters something to cheer against Munster. We want them to come here and to enjoy the whole experience and, importantly, we want them to enjoy what happens on the park."
Wing Darren Daniel was today (Fri) undergoing a fitness test ahead of the Munster game.
Scarlets starting XV (v Munster, Nov 28) - 15 Morgan Stoddart, 14 Darren Daniel or Matthew Jacob, 13 Regan King, 12 Gavin Evans, 11 Jon Davies, 10 Rhys Priestland, 9 Sililo Martens, 1 Iestyn Thomas, 2 Ken Owens, 3 Kees Meeuws, 4 Vernon Cooper, 5 Dominic Day, 6 Nathan Thomas, 7 Simon Easterby (capt), 8 David Lyons. Reps - 16 Deacon Manu, 17 Mahonri Schwalger, 18 Phil John, 19 Rob McCusker, 20 Johnathan Edwards, 21 Gavin Cattle, 22 Ceiron Thomas.
Guinness PRO12
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