New York Stock Exchange Chief Executive John Thain has been picked by Merrill Lynch & Co. (NYSE: MER) to be its next CEO, according to media reports.

The New York Post, which broke the story, writes "The move is a huge coup for Merrill and board member Alberto Cribiore, who has led the search for a new CEO after (Stan) O'Neal resigned on Oct. 30."

But Merrill's quick move is bad news for CItigroup Inc. (NYSE: C), which had wanted to hire Thain to replace its unpopular (and now ex) CEO Chuck Prince, the Post says.

The move is unexpected, according to the Wall Street Journal [subscription required], which said "insiders on Wall Street" had speculated that BlackRock Inc. CEO Larry Fink would get the job. CNBC is reporting that Fink was offered the job but turned it down.

Thain's departure from NYSE Euronext (NYSE: NYX) isn't a shock. He viewed the job, which he got after the departure of Richard Grasso, as a public service, according to the Journal. Shares of Merrill Lynch, down more than 35% this year, rallied on the news, rising $2.82, or 5%, to $59.75. NYSE Euonext and Citigroup were little changed.

The reshuffling of Wall Street's top management is far from over. Watch this space.