Jonathan Fox, who was Grey's EVP and CEO for the region from 1997 to 2000 and currently its New York-based vice-president of global business development, will assume interim duties until a replacement is found.
The sudden departure of the 20-year Grey veteran took the industry by surprise, particularly as Rosenkranz was widely seen as a likely candidate to succeed the group's chairman, president and CEO, Edward Meyer.
However, both Rosenkranz and Grey officials denied that any specific issues prompted the departure. "Eric is leaving with our deepest appreciation and thanks for what he's done," said a company spokesperson in the Hong Kong office.
Under Rosenkranz's guidance, the regional operation achieved record profit growth from 2000 to 2003.
"I've had a sensational 20 years at Grey. I think Grey is a fabulous company and I really enjoyed my time there," said Rosenkranz, who declined to comment on his future move.
Fox will lead the search for Rosenkranz' successor. "It is a big role to fill because of our strength and determination to add resources in the region," said Fox. "Our goal is to have recommendations on a new management structure for the region in the near term."
Fox confirmed that the search would look at both strong internal and external candidates.
"Given the fact that Grey is a major player in the region, we are highly attractive to potential outside candidates," said Fox.
Commenting through a spokeswoman in the company's New York office, Meyer said: "(Grey) views Asia as the single most important and fastest area of growth in our network and we are in the process of redoubling our efforts within the region."