Italian debutants Atalanta claimed third place in Serie A and a spot in the Champions League last season after a thrilling campaign that saw them finish as the leading goalscorers in the Italian top flight.
But their hopes of transferring that form to European club football's top competition suffered an early blow with a 4-0 thrashing at Dinamo Zagreb.
It was only a second win in 25 Champions League group-stage matches for the Croatian champions, and leaves Atalanta with plenty to do to get out of a group which also includes tournament favourites Manchester City.