Foster produced a crucial double save during Saturday's 3-0 win over Blackburn, a result which effectively ensured Albion another season of Barclays Premier League football.
Foster's future is still very much in the balance, with Birmingham waiting until the end of the season to make a decision on his transfer status, but Ridgewell knows keeping him at the Hawthorns is crucial.
The Albion defender said: "I think the whole team would like to keep Ben Foster. If we want to take this club forward, we've got to keep the likes of Ben Foster and he is a great player for us.
"I sense Ben would like to stay here. I know him well and he is settled here and hopefully the club can keep him and Albion can sort it out.
"He is a Birmingham player but it is a different team to when he played there. I'm sure Ben would like to stay here and keep playing here because he is doing really well."