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

UnitedHealth Group shares rebounded modestly Wednesday following yesterday's crash, with analysts from UBS, Oppenheimer, and Morgan Stanley leaving their ratings unchanged after the health insurer pulled its outlook and announced its CEO had stepped down.

May 13 (UPI) -- UnitedHealth Group announced Tuesday CEO Andrew Witty will step down, citing "personal reasons." Witty will leave the role of CEO and be replaced by Stephen J. Hemsley, effective immediately.

Witty’s departure was surprising, though it follows a sharp downturn in the healthcare juggernaut’s financial outlook. He is being replaced by Stephen Hemsley, the chair of UnitedHealth’s board and a previous chief executive.

UnitedHealth Group faces a U.S. Department of Justice criminal investigation for potential Medicare fraud, as reported by the Wall Street Journal. This follows CEO Andrew Witty's unexpected departure and a suspended financial forecast due to rising medical costs,

UnitedHealth Group CEO Stephen Hemsley, who replaced Andrew Witty, said he has the right strategy in place “for the era ahead.”