Citigroup has announced that Robert Druskin, the head of Citigroup's corporate and investment bank, will become the bank's chief operating officer. That slot has been empty since Robert Willumstad departed last summer. Druskin's main job appears to be cutting costs. Also, Michael Klein and Thomas Maheras will become co-presidents of the corporate and investment bank; Druskin will retain the CEO title. The announcement seems to be aimed at symbolically nodding to the issue of costs, ending uncertainty among Citigroup's investment bankers, and putting an end to the rampant talk that Sallie Krawcheck, the chief financial officer, is poised to leave. That would be a momentous event, and the bank is working hard to combat the rumors.

For more on Druskin:
- here's a New York Times article