The Croatian striker, who scored 11 goals in 14 matches at the end of last season, has failed to find the net in his last nine games for the Toffees.
"The team need him," Moyes told reporters. "I said last week a lot of what we do this year will be determined by how well Jela scores between now and the end of the season.
"He needs to get a goal but I don't know if one goal will make everything right. If I saw him getting four goals in four games then I would start to think 'This is what we want'.
"You have to find a way of making that happen again but we could do with him standing up and getting us some goals now."