In monsoon conditions at Rodney Parade, Scarlets came out on the wrong side of a tight, edgy contest that went down to the wire.
A disallowed try and a couple of late misses at goal proved the difference in the East v West Welsh derby, with the Dragons celebrating a 13-12 victory at the close.
Scarlets will feel they should have emerged with the win, particularly after dominating the final exchanges.
But just like six days earlier against the Ospreys, they were left to rue missed opportunities.
Biblical rain across South`Wales meant this was never going to be a classic to usher in the new year.
Errors and discipline were always going to be key.
With the elements in their favour in the first half, it was a much-changed Dragons who struck first, full-back Cai Evans opening the scoring with a fifth-minute penalty. Evans then missed with another attempt from halfway as the early territory and possession belonged to the home side.
Unsurprisingly, with the rain hammering down, the boot was dominating proceedings and a brilliant 50:22 by returning fly-half Sam Costelow set up an attack which led to the game’s opening try.
Ryan Elias and Vaea Fifita made the initial dents before a lovely weighted pass by Costelow freed Ioan Lloyd, who put Tom Rogers in enough space to cut inside and dive over. Costelow nailed the conversion to make it 7-3.
Dragons, though, were back in front on 36 minutes. With discipline letting the visitors down, the Men of Gwent had an attacking line-out close to the Scarlets line and following a couple of pick and drives, Wales international Aaron Wainwright celebrated his 100th appearance by burrowing over. Evans added the extras to make it 10-7 at the interval.
A strong line-out drive by the Dragons eight led to Evans extending the lead with a second penalty success on 48 minutes.
It continued to be a cagey affair with handling errors letting the Scarlets down at key moments.
With 15 minutes left on the clock they did manage to set up camp inside the Dragons 22.
Cheered on by a vocal travelling support, Rogers went close to a second, but with the referee playing penalty advantage, back came the Scarlets for an attacking scrum. Fifita carried from the base and with the home defence stretched, a clever change of direction saw Lloyd pierce the defence to cross. Costelow was wide with the conversion and the Dragons led by a point going into the final 10 minutes.
A sensational break from Lloyd set up another assault on the Dragons line and after the forwards had patiently banged on the door, Fifita thought he had the ball over the whitewash. However, the TMO adjudged no try and from the resultant penalty, Costelow pushed his kick wide.
There was still time for one last attack, but the Scarlets spilled possession inside the Dragons 22 and the home side were able to clear their lines and with it secure a second victory of the URC campaign.
Next up for the Scarlets is a trip to France to play Clermont Auvergne in the third pool round of the European Challenge Cup on Saturday, January 13.
Dragons – Try: A. Wainwright. Con: C. Evans. pens: Evans (2).
Scarlets – Tries: T. Rogers, I. Lloyd. Con: S. Costelow
Scarlets: Ioan Lloyd; Tom Rogers, Joe Roberts (repl Jonthan Davies 73), Johnny Williams, Steff Evans (repl Ioan Nicholas 27); Sam Costelow, Gareth Davies (repl Kiern Hardy 60); Kemsley Mathias (repl Wyn Jones 47), Ryan Elias, Sam Wainwright (repl Joe Jones 60), Alex Craig, Morgan Jones (repl Jac Price 51), Ben Williams, Josh Macleod (capt), Vaea Fifita (repl Shaun Evans 75).
Referee; Craig Evans (WRU)