Actually Salernitana is not strong opponent team for Juventus because in domestic league their current standing dropped to 20th position and have two winning of 18 matches, its good opportunity for Juventus face weakness teams on 16 round of Copa Italia and lead to quarter final against Frosinone on Friday, 12 January. In Copa Italia seems Juventus have bigger chance for winning trophy because top teams left such as AC Milan or Atalanta will face each other on quarter final round and other top teams left between AS Roma or Lazio have to fight on quarter final too.
In Coppa Italia, I agree that Juventus have good chance to lift the cup even it is not their priority. Juventus in theory are stronger than those clubs in Coppa Italia and if they play with their best performances, they will become a champion there.
Back to Serie A, after this match, Juventus will wait for Inter Milan's slippery performance to take over the first position in coming weeks. Especially, Champions League will return and Inter Milan will have like three to four matches in Serie A without best focus as they will be distracted by two big matches with Atletico Madrid.