Just three weeks ago, the winger was part of the Hadjuk Split side that was beaten by the Toffees in the playoff leg of the competition.
"I'm really looking forward to it," said 19-year-old Vlasic.
"I've never played in the group stage of the Europa League before, so it's exciting. It is something new and a good challenge.
"We need to forget about Saturday's loss to Tottenham and look ahead, prepare ourselves and I hope we can get a good result."