"It was a fantastic moment for me and for the team. Before I came onto the pitch the manager was telling me to give the game some energy," said the Dutch international.
"He said I have done that every time I have come off the bench and said to try and do the same this time. The fact that the goal came towards the end of the game was very good for us because it meant they did not have too much time to equalise.
"This is a new season and we want to get off to a good start, so this is an important goal for me and the team.
"Hopefully I can score more important goals because there are a lot of games still to play and a lot of points to play for.
"But it's always nice to score a goal against a big opponent, especially Manchester United, and I suppose it is an even better feeling when you've only come into the game late on as a substitute.
"We want to be able to compete until the end of the season and you have a better chance of doing that if you win games like this."