So he would have had no work or contract at Rangers. He could easily sign for another club. I suspect there would have been plenty of clubs that would be interested in signing a player for free but valued at £9m by Spurs!
Exactly how did Alan Hutton have his arm twisted to move from a club? At the end of the day, it was still his decision whether to sign or not. In hindsight, bearing in mind Rangers relegation to the lower leagues, it was a good move to make as he is probably set for life having played for...
Your analogy is completely misleading (and probably deliberately emotive) as in slavery the individual has no choice where they work whereas in football the player has ultimate choice.