What are the chances that some pork I bought in the supermarket had gone bad?

I bought it over the weekend and it said "FRESH" in big letters on top (as usual) and I put it into my freezer as soon as I got home. Today I took it out and defrosted it in the microwave and its giving off a funky smell. It doesn't smell rotten, per se, just a little odd. Do you think its just because I microwaved it?