Grigg, just four days after notching a hat-trick in a 3-0 victory at Carlisle, has now hit 16 goals for the Saddlers this term after his first-half penalty and second-half strike.
Smith said: "It's not just his goals, its his work-rate too. He is a lad who wants to get better and he has good technique. You never think he is going to miss a penalty."
Smith revealed he is talking to Grigg's representatives with a view to extending his contract, which expires in the summer.
"He needs another season with us under his belt, and if he does that he can play where he wants," Smith said.
"If clubs come in with an unbelievable offer you have to listen, but if he goes to a big club now he is not going to play and develop as he is with us. He needs to maintain his development."