Very little happens at Chicago-based Citadel Investment Group without the say-so of Kenneth Griffin, its intense founder and CEO. And, sources say, the departure of Rohit D’Souza was no different. The former head of global equities at Merrill Lynch was brought in a year ago to build Citadel Securities, the firm’s new investment banking and securities trading arm. In a letter to clients last month, sent shortly after the announcement that D’Souza would be leaving, Griffin said he is extremely pleased with the progress the business has made: "I am very proud of the work that has been accomplished by those running day-to-day operations."

Now that the architect’s work is done, as Citadel Securities enters the execution phase, Griffin has turned to Patrik Edsparr, president of Citadel Europe, who will take over from D’Souza. Edsparr, who has an MBA from the Stockholm School of Economics, was hired by Citadel last year from JPMorgan Chase & Co., where he had been global head of proprietary trading.