F/t rat smells awful. is that normal?

Bought a small frozen rat to feed my python. The package had popped when I took it out of the freezer in the pet store. Now I've opened it up to thaw it and it smells terrible. I'm used to the mice smelling but this was gross. Is it normal for the rats to smell when defrosting? do you think its safe to feed my python? do the frozen rats ever go bad in the freezer?