Here's the thing. Let's say it does taste like old, freezer burned, funky beef. You cooked it, it falls on you. At that point, are you willing to tell everyone that their supervisor gave you 4 year old meat to cook and serve to them. The product was already flawed at that point.
It's a tough call and you might end up holding the bag on it.........literally! You risk taking a hit to your credibility because of the old beef you were given to work with.
He should be pulling out the prime rib roasts! But that's just me.........