Not sure what kind of opportunities he was talking about as far as doors opening. But I can tell you this much, if he does go get his MBA - the first year salary coming out (after spending $130K and 2 years lost wages getting it) is about half the minimum NFL salary. If he has a passion for the game, I don't know why he wouldn't try to join a team and give himself a shot for a year in the NFL to see how he measures up.
I'll tell you what - I don't want him playing here now. Any player that allows others to define how good he is ("not getting drafted is a good indication [that he's not cut out for it]"), doesn't have the heart I want to see. Can you imagine a guy like Zach Thomas ever saying "well if no one else believes in me they must be right". If you think you're good enough then you shouldn't listen to others, put yourself in a position to prove them wrong.