Jagielka insists that defenders across the Premier League will have studied the 27-year-old's traits in the penalty area, and that Jelavic must now find a way to thrive regardless.
He said: "It's what happens in the Premier League.
"You've got people watching you and with no disrespect to what has happened at his other clubs, when he came in nobody really knew what he was going to do.
"Some of the first touch finishes that he had last season were brilliant.
"Whether he can do that week in week out for a longer period you never know.
"They'll have a rough idea of where he stands and where he wants to receive the ball, which makes Jela's job harder.
"People are talking as if he's only got one or two but he's got seven. It proves how well he did last season and it's better when people are talking about you rather than not. He's got all of our backing and we're all hoping it's only a matter of time before he's scoring every week and challenging to be top scorer."