With Claudio Yacob back following a hamstring injury, Foster believes that the Baggies will have the upper hand.
"On our day we are a really good team," he said, "we go into every match thinking that we can get three points.
"And we can beat anyone on our day. The gaffer has got us playing some nice, attractive attacking football.
"There is a lot of pressure on derby matches, but we will go into this in in a confident frame of mind, thinking we can win - just like we do every match."