Foster pulled off a penalty save to help the Baggies to a 2-0 win.
Reid told talkSPORT: "He's one of the top English keepers and he kept us in it.
"He's brilliant. He's one that we spent big on, and we don't do that too often. But with performances like that you can see why we spent the money.
"Obviously the highlight of the saves was the penalty, which was top draw."