Smalling felt Hernandez reducing the arrears so quickly after Villa went two goals ahead was an important factor.
He said: "We managed to get that goal straight away and make an impact. We know we can play like that from the start.
"I don't know why we don't. It just took that kick up the backside to get us going, and luckily it paid off.
"We had to come out in the second half and put on a performance and luckily 'Chicha' (Hernandez) paid off with the goals.
"We knew there was still plenty of time left and that we can get two or three goals each game."