Corbat made the comment during a conference call on Monday with Wall Street analysts. Last week, Corbat announced that Forese, who had served as the bank's No. 2 executive, plans to retire after 34 years with the bank and its predecessor companies.
Francisco Aristeguieta, who led the New York-based bank's business in the Asia Pacific region, also plans to depart for an outside opportunity.
Citigroup on Monday posted better-than-expected results for the first quarter as a steep cut in the U.S. bank's effective corporate tax rate helped to offset a fall in stock-trading revenue.
The shares slipped 1.2% to $66.59 in trading Monday.