The 25-year old Croatian has picked up this season where he left off last campaign, scoring twice in the opening three Scottish Premier League matches, and McCann feels he is an extremely important piece of the Rangers puzzle.
Ahead of Thursday night's Europa League qualifying first leg against Maribor, the Sky Sports pundit says that Jelavic is indeed the main man at Ibrox and his fitness could hinge on how they perform this season.
"For me Jelavic is the Rangers talisman these days," he said.
"I reckon (Ally McCoist) Coisty must lie awake at night just hoping Nikica is OK when he turns up for training the next morning.
"Rangers need the big man fit and playing.
"He's such an important player and I just don't think Rangers would cope if they lost him.
"They didn't replace Kenny Miller when he left last winter and it's just as well Jelavic is back fully fit following his ankle injury.
"Coisty will be praying he's still at Ibrox by the time the transfer window closes.
"Obviously, Rangers are looking to bring players in and that's a major priority right now.
"But losing their key men must be a worry for the manager. The last thing Coisty needs is for some big club in England to wave their chequebook in the next couple of weeks."