Napoli Winger Manolo Gabbiadini bagged two in the first-half, following Jose Callejon's opener and Argentine star Gonzalo Higuain then completed the scoring in the final minutes of the game.
Martin Pusic with the sole goal for the Danish outfit.
Mabil was a 73rd minute substitute for Mikkel Duelund. The 20-year-old Aussie striker was snapped later with a souvenir - the shirt of Callejon.
Meanwhile Tom Rogic was an unused substitute as Celtic lost 3-1 away to Molde - a match that saw Celtic's Kris Commons angrily react on the bench to being subbed off.
And former Sydney FC marquee Marc Janko played a full game in Basel's 2-1 home loss to Belenenses.