The Baggies won 1-0 through Kyle Bartley's effort.
On Dunk's disallowed goal, Potter said: "As far as I know Lewis Dunk asked take the free-kick quickly and the referee said yes. In between that there was another whistle. I don't know what that whistle was for. It would be nice for a bit more clarification. I don't know what the second whistle is for. I don't understand that.
"The confusion is on the pitch and it gets worse when someone outside this area is making the decisions. It is what it is. We've not helped ourselves with the two penalties so I cannot put it all down to that [disallowed goal].
"We need to improve and get better at that [taking penalties]. We're never going to get two better chances. We have to stay calm."