THE transfer window opened at midnight. Some Premier League clubs will opt for wholesale alterations. Others will look to tweak. And the seven managers still in European football know they can only swap three players in their Champions League or Europa League squads — although now there is no “cup-tied” rule to worry about. Here, SunSport looks at the key questions in the January window.CLOCK RUNNING DOWN The list of top-grade players entering the final six months of their deals is a huge headache for a number of clubs. At Spurs, Jose Mourinho persuaded Toby Alderweireld to sign a new contract after nearly two years of umm-ing and aah-ing but Christian Eriksen and Jan Vertonghen are still to decide.Others who can now agree pre-contract deals with non-English clubs include Adam Lallana at Liverpool, Manchester City’s Fernandinho and the Chelsea pair Willian and Olivier Giroud. It means the players are in control of their situation, rather than the clubs. But for any chairmen looking to get something back instead of seeing the players leave for free in the summer this is the final opportunity to find a buyer, even if it means a cut-price fee. Vertonghen, Fernandinho, Lallana and Willian could…