Mahrez has stayed away from the club this week after being blocked from joining Manchester City last week.
The midfielder has Madjer's sympathy, who stated: "It's true that Mahrez deserves better now than Leicester. But we must not forget that it was Leicester who put him on the right track. I think a serious conversation with his leaders is needed.
"He wants to go to a bigger English club. I do not know what really happened about his transfer.
"Me, I advise him to resume training and work hard, even if the transfer failed. And we must not forget that there are the matches of the national team coming soon (in March) and a preparation that will be done. May he come back to us in great shape. I hope that later doors will be opened for a bigger club."