It was a crisis that brought Don Nathan to UnitedHealth Group.

While working as a partner with Robinson Lerer & Montgomery in 2006, Nathan was asked to work with UnitedHealth Group, a client of the firm, after a Wall Street Journal story reported that then-CEO William McGuire had been backdating stock options.

Within a year of the story's publication, McGuire had resigned and Stephen Hemsley had been named president and CEO.

Hemsley turned to Nathan, asking him to consider a ...