If you completely stay away from the football topic, and avoid using the NFL's trademarks, you might be able to stay away from a lawsuit. I myself wouldn't look at registering them. Especially since when parking domains, you usually want to relate to the name of the domain in the content.
Better luck next time..If you found this information helpful, I do appreciate Rep points
I dont think law suits will happen unless you're in competition for space :P Look back at Microsoft vs Mike Rowe haha then ended up paying him for the domain. I say take the chances