Man United made it two wins out of two this season thanks to Adnan Januzaj’s goal but they were poor during the match.
Van Gaal insisted United will need time before they can show what they can really do this season.
“There is still a long way to go. You cannot expect it with only four weeks preparation. You need more matches to come in the form I think we can show,” he said.
On top of this, players such as Robin van Persie, Nani and Angel di Maria have left Old Trafford.
The new signings will need time to buy into van Gaal’s way of thinking and how he sets up his team. They will have to do so quickly as United have a number of fixtures coming up this month including the Champions League playoff tie with Club Brugge.