Gagging is too mild. Hagel would be a disaster. I am retired military having been both enlisted and officer. I have always disliked this idea that because someone had a military background and/or combat experience is better suited lead the military. Too many who are considered have experience like Hagel, a tour of combat are incompetent to lead anything. Serving in the military, even for a career, does not make you qualified to lead the military. Generals like Powell or Clark are political climbers who achieved high rank by way of influence both inside and outside of the military. Should you have a basic understanding of the military — absolutely but you also need to understand history and a lot of other things as well. The best suited civilian to be SecDef might be a senior analyst, a business leader with proven LEADERSHIP skills not just management skills. Leaders lead people, managers manage things and processes. Within the military most of the time the real leaders rise no further than field grade because they are leading instead of making political connections and doing all of the right jobs.
I noticed Powell never got a division command. He admits some serious errors during his assistanct division command period at Fort Carson.