This is like musical Defense Secretaries the way the Pentagon keeps going through them:

Defense Secretary Chuck Hagel is stepping down under pressure from President Barack Obama’s Cabinet, senior administration officials said Monday, following a rocky tenure in which he has struggled to break through the White House’s insular foreign policy team.

Hagel is the first senior Obama adviser to leave the administration following the sweeping losses for Obama’s party in the midterm elections. It also comes as the president’s national security team has been battered by multiple foreign policy crises, including the rise of the Islamic State militants in Iraq and Syria.  [Associated Press]

You can read more at the link, but I would be surprised if Michelle Flournoy is not nominated because she should be capable considering all her time at the Pentagon, is a strong Democrat supporter, and also brings political benefits. First of all she would be the first female Secretary of Defense and if the Republican controlled Congress does anything to try and block her nomination it can be played as the “War on Women” by the Democrats in anticipation of the 2016 elections.