If not, you will be required to take leveling courses to get you up to speed. If your undergraduate degree is in management or HR, the MBA would do you a world of good. My MA is in HRD, but after being in an MBA program for a while I can definitely say that my eyes have been opened. I'm going to stick my neck out, here it goes. An MBA concentrates on the bottom line.
People are secondary.
The concern for people and the concentration in HR will probably not consider issues of right and wrong, good versus bad practices. HR Management also cares about the bottom line but takes a much more people centric view. The individuals who make up an organization are our charges. We must balance the good of the organization with the good of the workforce. In HR we are advocates for employees and representatives of the company.