Ceri Sweeney notched all ten of Cardiff's points with a try, a conversion and a penalty but the Scarlets were better throughout and deservedly edged the contest.
Wales coach Warren Gatland looked on worryingly as Halfpenny failed to return after the restart but Young insists his ankle injury is far from serious.
"I don't think there is anything that should keep Leigh out of international duty," said Young.
"But he is certainly going to be sore for the next couple of days."
In other Magners League action, Newport-Gwent Dragons host fellow strugglers Aironi today while Ospreys travel to Glasgow in Sunday's clash.
Dragons welcome back fly-half Jason Tovey for the first time since he tore a hamstring against Glasgow on September 12, as they seek their second victory of the season against their winless Italian opponents.