The England international believes it is only a matter of time before his struggling team-mate starts scoring regularly again to maintain the Toffees' top-four charge
Last season Jelavic proved a revelation in England following his January move from Rangers, scoring 11 goals in 16 games as the Toffees surged to seventh in the table.
This term goals have been harder to come by for the Croat, who has netted just five times, and only once in his last eight matches.
But Jagielka is adamant his team-mate's quality will eventually shine through again, comparing his recent struggles to those of another of last season's breakthrough stars, Newcastle's Papiss Cisse.
"Everything was working for him when he came and now the person who is playing up front with him - Felli - everything is coming off for him," he told the Liverpool Echo.
"Look up at Newcastle. Demba Ba was on fire then Papiss Cisse came and Ba didn't score. This season it is the opposite way round. That is the way cycles go.
"We'd love to have both Felli and Jela firing on all cylinders but it's not like Jela is getting into four or five good positions and missing easy chances every game. It is just not breaking for him.
"He knows we're supporting him and he'll get frustrated on the days it doesn't happen but we know he'll come good.
"And, at the moment we're doing OK without his goals so when he does hit the ground running again, he'll make us even stronger."