The Eyasses lost to the Scarlets in awful conditions at Llandarcy Academy of Sport on Wednesday evening.
In a game dominated by the conditions, there was just the one score separating the teams at the end, the rain, hail and wind making it difficult for both teams.
It was the Scarlets who opened the scoring through the boot of Daniel Jones on 11 minutesm only for Luke Price to level four minutes later.
The Scarlets retook the lead six minutes later through a penalty try after their lineout drive was halted illegally as they looked like to tumble their way over the line, converted by Jones, and although Young Ospreys prop Lewis Kirby was sinbinned shortly after, his team were able to hold out until the break without conceding.
Luke Price cut the deficit in the 48th minute, after Charlie Randall of the Scarlets was issued a yellow card, and although the Eyasses rallied as they looked for a way back into the game they were unable to find their way through, a second Jones penalty sealing a 13-6 win for the visitors.