The Hamburg boss has named the Holland international his new skipper after relieving previous incumbent Heiko Westermann of his duties
The Rothosen have lost three games in a row, including the 9-2 drubbing against Bayern Munich two weeks ago.
Fink, 45, made the change ahead of the side’s weekend fixture against Mainz, believing his former captain was under too much pressure and that Van der Vaart is the ideal replacement.
"Westermann's responsibility has become too much,” Fink told Bild.
"Van der Vaart now has to be an example and take on even more responsibility."
The former Basel boss believes the club's problems lie deeper than just who occupies the hot seat.
"In my one-and-a-half years here I have seen plenty at the club. Why in the past have so many coaches gone? If it goes bad, we are always looking for excuses,” Fink continued.
The former Bayern Munich player will hope his move will lead to three points against Mainz on Saturday.