Hedge fund wizard Edward S. Lampert is taking on a startling new role at Sears Holdings Corp.: chief marketer and merchandiser.

The billionaire chairman shook up top management at the No. 3 U.S. retailer Thursday after another poor quarter, naming Aylwin B. Lewis to replace Alan J. Lacy as chief executive and taking on a more direct role at the struggling company.

The moves come with sales still sinking at the company's two chains, nearly six months after Kmart Holding Corp.'s acquisition of Sears, Roebuck & Co. Reporting results from the first full quarter after the merger, Sears Holdings said it had a lower-than-expected profit of $161 million.

The news disappointed investors, who had driven up Sears' stock dramatically both before and after the March 24 merger engineered by Lampert. Shares in the company sank $7.04, or 5.2 percent, to close at $127.81 in heavy trading on the Nasdaq Stock Market, far off their peak of $163.50 in July.

Lampert, founder of Greenwich, Conn.-based hedge fund ESL Investments Inc., which takes large stakes in distressed companies, will direct the marketing, merchandising, design and online businesses of Sears Holdings as well as its Lands' End casual-clothing unit.

He named Lewis, the former head of Kmart and of Sears' retail business, to take over as chief executive and president of the Hoffman Estates, Ill.-based company effective Sept. 30. Lewis will have responsibility for the company's 3,900 stores as well as for the home services, finance, legal, supply chain, information technology and human resource departments.

Lacy, who stays on for now as vice chairman and a director, headed Sears Roebuck from 2000 until its acquisition by Kmart and was chief executive under Lampert for the past six months. His demotion was not completely unexpected, since he had failed to halt Sears' retail slide and had a diminished role under Lampert.

More surprising is the hands-on role being assumed by Lampert, who has made a giant mark in financial dealings but little in retail. Lampert made $1.02 billion last year at ESL Investments, according to the industry magazine Institutional Investor's Alpha.

Analysts were caught off guard by Lampert's expanded role and had mixed opinions on whether Lewis will fare better at Sears than Lacy did.

"Lewis is an operations guy," analyst Jim Cramer said in comments posted at RealMoney.com. "His real strength: developing stores that appeal to those who aren't the richest people on earth. For Sears Holdings, he needs to find a space between Wal-Mart and Target. I believe he can do it."