A big deal in trading has led to a Wall Street titan swapping roles

Robert Greifeld, former CEO of Nasdaq.Hollis Johnson

Robert Greifeld, the former CEO of Nasdaq, will become chairman of the board of Virtu Financial, a high-frequency trading firm, after it completes its $1.4 billion takeover of rival KCG Holdings.

Greifeld stepped down as CEO of Nasdaq on January 1 after running the company since 2003 and transforming it into a more diversified, transatlantic exchange operator. He stepped down as chairman of Nasdaq on May 10, according to a news release. Michael Splinter, the cofounder of WISC Partners, was elected by Nasdaq stockholders to replace him.

Greifeld will take over from current chairman and Virtu founder Vincent Viola. The company disclosed the move in a regulatory filing on May 31.

Greifeld, along with Silver Lake co-founder Glenn Hutchins, joined forces with Singapore’s GIC and Temasek and Canada’s Public Sector Pension Investment Board to buy a combined $750 million of new Virtu stock as part of the firm’s deal to buy KCG. Hutchins will also join Virtu’s board.

Viola, a former chairman of the New York Mercantile Exchange, had been nominated by US President Donald Trump to be secretary of the Army, but withdrew his name from consideration in February due to potential conflicts related to his businesses.

Along with Virtu CEO Douglas Cifu, Viola bought the Florida Panthers of the U.S. National Hockey League in 2013.