But the visitors escaped with a 40-35 triumph at Rodney Parade to make it back-to-back regional wins after their thumping triumph over the Ospreys as they came out on top in a breathtaking game of 11 tries.
It was the Scarlets who drew first blood when Ioan Nicholas ran onto a neat kick through by Ioan Hughes to grab the first try in only the sixth minute. By the break there had been half-a-dozen more as the visitors built up a 26-21 lead.
The Dragons A team responded with tries by Wales U20 centre Connor Edwards and the first of two from prop Josh Reynolds to edge ahead 14-7, but back came the Scarlets through a burrowing Jonathan Evans at scrum half to tie things up.
Reynolds then powered over for his second from a close range line-out before Nicholas picked up a loose ball and sprinted clear for his brace. The final word of the first-half came from Scarlets hooker Dafydd Hughes as he rode on the back of a driving line-out to make it 26-21 at the break to the visitors.
A second try from the impressive Edwards pushed the Dragons back into the lead, but then the Dragons lost hooker Rhys Lawrence to a yellow card for pulling down a driving lie-out. No sooner had he departed than the Scarlets won a penalty try from a similar procedure.
The final Scarlets try came from Tomi Lewis, along with a fourth conversion from Hughes, but there was nearly a sting in the tail. Dyer was sent clear, but then called back and David Richards gave the Dragons the final word with his side’s fifth try.
Ben Cambriani flew in for two tries as the Ospreys Development team got their Celtic Cup campaign off the mark with a comprehensive 29-5 win over Cardiff Blues A at Bridgend.
The Wales U18 and Wales Sevens wing struck twice in the first half after the Blues had taken the lead with a try from lock Teddy Williams. Josh Thomas converted the second Cambriani try having earlier kicked a penalty to give the home side a 15-5 interval lead.
The Ospreys wasted no time in building on their half-time lead and when a dominant scrum in the Blues 22 won them a penalty, Thomas stepped up to land his third kick of the game. The home outside half added another when the Blues were penalised for side-entry at a ruck and then he completed his second half-trick when the Ospreys scrum earned another penalty.
That made it 24-7 with 10 minutes to go and there was a final flourish for the home fans to enjoy as Travis Huntley ended a multi-phase move with his side’s third try. Having drawn in Munster in their opening game, it was just what the Ospreys needed ahead of their game with reigning champions Leinster A at St Helen’s on Friday.