NAC agreed to release Arijanet Muric from his loan so he could return to parent club City as cover for the injured Claudio Bravo.
"Due to the injury of the second goalkeeper, Manchester City came into a situation that we had not anticipated beforehand," explained Smulders.
"Despite looking at other solutions, we ultimately had to decide to return Aro to Manchester. Having a partnership also means that you try to help each other in these situations.
"We help Manchester City with the return of Aro and of course City Football Group helps us to solve the situation that has arisen in goal at NAC. It is certainly not how we envisaged it, but I am convinced that NAC will ultimately emerge stronger from this situation."