An unexceptional game erupted into a frantic conclusion as the Dragons, who had spent most of the afternoon fumbling, held on to the ball for 35 phases in a six-and-a-half minute spell in stoppage time. But they were unable to score and so surrendered their unbeaten home record.
It was the Scarlets' first away win in the league since May and it was all the more remarkable considering their lengthy injury list, which grew further when the Wales and Lions fly-half Stephen Jones hurt his shoulder in a collision with his opposite number, Shaun Connor. Jones is not expected to be out for long, but the Christmas programme of Welsh derbies has also resulted in James Hook and Alun Wyn Jones suffering shoulder injuries.
The Dragons were also missing key players, but that did not explain the basic errors that disfigured the game. Passes were dropped or thrown forward, players got in each other's way and decision-making was suspect throughout. The Scarlets scored the only try and were denied another when Andy Fenby lost control over the line. Their centres, Jonathan Davies and Sean Lamont, were too good for the Dragons' defence, but there was an absence of genuine class.
Davies created the try on 23 minutes, shrugging off Matthew Watkins to give Rhys Priestland a run in from 30 yards. The Scarlets were threatening to run amok but they struggled at the breakdown, conceding numerous turnovers, and after taking the lead early in the second half they opted to preserve what they had and invited the Dragons on to them.
It looked a sure strategy, given the problems the Dragons had holding on to the ball, but in stoppage time Fenby filled in at scrum-half in his own 22. He lobbed a pass to Dan Evans that took so long to arrive the clearance kick was charged down. The Dragons had the base from which to launch their final wave of attacks.
The Scarlets are still one off the bottom of the Magners League but they are now within touching distance of Cardiff Blues and the Dragons. In previous years, finishing the season as the lowest Welsh region mattered little as far as Heineken Cup qualification went, but only three of the four sides will make next season's tournament. Defeat would have left the Scarlets adrift. "The move is good for the league because it makes it more competitive but it is bad for coaches," said the Scarlets' head coach, Nigel Davies. "We knew we needed a result."
Despite missing eight players through injury, including the Lions hooker Matthew Rees, Davies dropped the scrum-half Martin Roberts after his sledging had cost his side three points in the Boxing Day derby against the Ospreys.
The Dragons lost four matches in December. "We made too many unforced errors," said their head coach, Paul Turner. "The commitment was there, but that will only get you so far. Execution and accuracy are what win matches."
Turner's side led three times but they failed to score in the second half and the headless nature of their final onslaught said everything about their afternoon.
Newport Gwent Dragons Tovey (M Thomas, 68); Brew, Riley, Watkins, Fussell; Connor, Lee (Williams, h-t); Gustafson (McKenzie, 63), Willis (capt; S Jones, 58), Palmer, Sidoli, Charteris, MacDonald (Webb, 58), G Thomas, Evans.
Pens Connor 2 Drop goal Connor.
Scarlets Priestland; Williams, Lamont, J Davies, Fenby; S Jones (Evans, 55), G Davies; John, Owens, Manu, Reed (Welch, 59), Day, McCusker, Edwards (Pugh, 62), Lyons (capt).
Try Priestland Pens S Jones 2, Priestland.
Referee N Owens (Pontyberem). Attendance 6,429.
