Raul, who arrived in Gelsenkirchen in 2010 after spending 16 seasons at Real Madrid, will be out of a contract at the end of the season and has been linked with a move to Qatar.
"It would be a shame for Raul and the club [if he left]," Fischer told Goal.com. "He is a nice figure.
"Several things are in the media but whether it's true or not, I do not know.
"We are of course going to [finish] fourth, no question, but we have to work hard. This is the most important thing for us."
Raul has scored 14 goals in 29 games for the German outfit this season.