The Belgian struck the woodwork in the 2-1 triumph.
“I wanted to score a goal, but we still won and picked up three important points," Mertens told Mediaset Premium.
“We mustn't forget that Dynamo are a very strong side and today we did deserve the victory.
“In my view Sarri is a great Coach and is doing a wonderful job. It's a pleasure to play for Napoli."