Like Michael Olise's sale to Bayern Munich last summer, Eze's imminent move to Arsenal will mean Glasner having to change Palace's system to accommodate.
Asked if Romain Esse can replace Eze, Glasner said: "Not now, honestly not now. Then we don't need a signing but Romain played for six months at Millwall, he was good and we brought him in but now it's about making the next steps to be ready for Premier League football consistently. Not once or twice, we need a player who is consistently performing.
"Again, I'm worrying about Crystal Palace, if I asked you when I arrived who are the most important players in Crystal Palace's attack you say Eberechi Eze and Michael Olise. Both are gone and then you need to replace them. Even at that time, I wouldn't be sitting here if the club had been successful, they were playing against relegation for two years in a row - even with these two top stars.
"If we don't do the right things now, I'm worried that it can go very quickly in the wrong direction. When I see what's happening around us, even more.
"Dean Henderson said it before the Frederikstad game we lost Michael and we couldn't replace him because he was too good. But with a different profile and slight change to the way we play - we can replace him and that's what Ismaila Sarr did. He's not Michael Olise but he helped us achieve the best season in Crystal Palace history."