The Holland midfielder, however, remains adamant that winning silverware must be City's target next season.
De Jong said: "Last season was successful, of course it was. But you have to be realistic as well. It was our first season with the new squad, I think we're used to each other now and next season will be even better.
"There is always a risk that more new players this summer will make it difficult again next season.
"But you never know, there's something about every person, what kind of mentality and what kind of discipline he brings to the team, and how far he will want to go to perform for City."