Rodgers had hoped Vardy would be fit to return to action after the recent international break but ahead of Thursday's Europa Conference League quarter-final clash with PSV Eindhoven, he indicated Vardy would need further medical examination.
"I just had a quick chat with Jamie," revealed Rodgers.
"He has been running outside in straight lines but he was just maybe opening up the MCL (medial collateral ligament) when he was striking the ball.
"He was getting a little bit of pain in that. I'll have to speak with the medical team to see where that's at, but it doesn't sound as if he's too close to being back. It's hard to put a time line on it. There is an issue so we have to get to the bottom of it."