When is it not? I mean really? A pro has only so many years he can play. If you were that pro wouldn't you want to make the most of your career? If you were offered a lot of money for your job wouldn't you move? Yes, there are other aspects to the decision; family, friends, etc., but ultimately we all look out for ourselves. Why should an athlete be any different? Let's face it, a team would ax a player in a minute if they thought they could do better.