The 35-year-old defender has rarely been able to string games together over the past few seasons because of chronic knee and ankle problems and is now seen by his boss as merely a back-up.
Former Manchester United centre-back Brown signed a one-year deal with the Black Cats in the summer but will only make appearances for the Wearside club if they are in desperate need.
"Wes has a different role this season," said the Dutchman.
"We're only going to use him if we really need him. He's fit, yes."