The 25-year-old Sweden international, who is out of contract in June and could leave on a Bosman transfer after five years at St Andrew's, has told Blues manager Alex McLeish he has not made his mind up regarding the future.
Ridgewell is in no doubt that Larsson, who scored the opening goal in Saturday's 2-0 Premier League win over Sunderland, would be difficult to replace.
He said: "I hope he stays, of course. He is a great player. Hopefully we can keep hold of these great players if we want to try to build on this team and this great club.
"We've won the Carling Cup and hopefully we'll stay in the league. If we want to build on this club, we've got to keep good players like that. Hopefully they can sort out with Seb to keep him here.
"His delivery from dead balls is deadly. You are going to have pay £10-15 million for a player like that so hopefully we can keep him.''
Ridgewell has been full of praise for the way Larsson has continued to perform at his best amid the uncertainty over his future. He received a standing ovation from Blues fans when substituted late on against the Black Cats.
Ridgewell said: "The fans have always been behind him. It's just a sticky situation with Seb at the minute. Everyone is glad to see it doesn't affect him. Everyone knows there are things off the field that can't be helped but he has been fantastic.''