The Croatia international netted 11 times in just 16 appearances for the Toffees last term after joining from Scottish side Rangers but just six so far in 2012-13 and is on a current run on two goals from 10 league games.
However, the former Red Devils midfielder is sure that the 27-year-old, who he labels as one of the best strikers with whom he has played, will find his killer instinct sooner rather than later.
|9/2||Nikica Jelavic is 9/2 with William Hill to score in an Everton win over West Ham
"The vein of form he had when he first came was special and from a football point of view I think we knew he couldn't keep it up constantly.
"Every striker goes through a lean spell but it hasn't taken him too long to score again. He's definitely up there with the best goalscorers I've played with, to be honest. His finishing is unbelievable."
The 25-year-old explained how the Croat's movement makes his own job much easier, observing how his clever runs make the passes pick themselves.
"He makes some great runs and he makes the passes easier for me," the Irishman added. "He makes my decision for me by his movement."