The Baggies have endured some poor recent form that has seen them fall to seventh place in the Premier League table, but Foster is hoping to secure a derby win on Saturday to secure the bragging rights of the West Midlands for the club's fans.
Foster told the Birmingham Mail: "The main thing is trying to get the three points and I don't think any of the fans will care if we play awfully and get three points.
"For them it's all about going into work on Monday morning, seeing the Villa fans and rubbing it in their face.
"It's not about performances, it's about grinding out that win and that's all we're aiming to do."
Foster played for Villa's rivals Birmingham City before deciding to make the move to The Hawthorns.