UnitedHealth Group Chairman Stephen Hemsley is returning to helm the health care conglomerate once again. He will replace Andrew Witty effective immediately.

Hemsley, 72, had led the company for more than a decade until 2017 and is re-taking the reins following a series of setbacks.

Stephen Hemsley hasn’t been CEO at UnitedHealth Group in nearly a decade yet he’s never really left. Hemsley, 72, has remained chairman and a major shareholder in the health care behemoth — and now is back in the CEO suite and is expected to reinstate his brand of operational and financial discipline that turbocharged the company’s growth.

Stephen Hemsley ran UnitedHealth Group for more than a decade. It's a different company after four years with Andrew Witty in charge.

Former CEO and current chairman Stephen Hemsley is stepping back into the top job following the abrupt resignation of Andrew Witty, UnitedHealth said.

UnitedHealth Group's stock has plunged nearly 50% due to the CEO resignation, withdrawal of guidance, and ongoing legal issues, creating a potential buying opportunity. The stock is deeply oversold with an RSI of 15, trading below both the 200-day and 50-day moving averages, indicating capitulation.

Even UnitedHealth will struggle to overcome parasitic medical costs that Warren Buffett once called a tapeworm eating away at U.S. economic competitiveness. The $300 billion healthcare conglomerate reinstalled Chairman Stephen Hemsley as CEO and yanked its financial guidance.

Shares of UnitedHealth Group fell after The Wall Street Journal reported that the Justice Department is investigating the company for possible criminal Medicare fraud. The stock fell 5.1%, to $292.40, in postmarket trading. Through Wednesday's close, shares have lost more than 40% of their value in the past year.