Foster recently ended his self-imposed international exile, two years after calling time on his England career, and is set to earn a place in Roy Hodgson's squad for the upcoming World Cup qualifiers against Montenegro and San Marino.
Foster's recent performances for the Baggies have been excellent and he is even being tipped in some quarters to usurp Manchester City's Joe Hart as England's number one.
Routledge knows just how big a barrier the former Manchester United and Birmingham man will be to Swansea's hopes of victory.
He said: "He is a very good keeper, some of the saves he made against Chelsea the other day were just world class.
"He is more than capable of performances like that and he is up there with the best, he is a top quality goalkeeper.
"If he wants to go back to play for England he more than deserves a place in that squad.
"We know it is going to be very tough this weekend. They have played some good football at home, we got a few early goals when we beat them here but this will be very different.
"We are in a battle against each other in the league, so it would be nice to come away with something."
- Sports & Recreation