John Mack has been selected as the new chairman and CEO of Wall Street investment bank Morgan Stanley, replacing the ousted Philip Purcell. For Mack, the return back to Morgan Stanley is especially sweet: four years ago, he lost a power struggle with Purcell to head the company.

The return of Mack is good news for the Morgan Stanley Old Guard -- but bad news for loyalists of Philip Purcell, says MarketWatch. Both Stephen Crawford and Zoe Cruz, appointed to the company's board by Purcell, will resign from their director posts. There could be more bloodletting on the way, according to rumors, as Mack re-installs a team of bankers loyal to him.