On each of his sets, Orson Welles, the legendary film director, would hire someone for the specific purpose of firing them in front of everyone. It was a tactic for asserting authority, for showing who is boss, and one that is not uncommon in football.
At Tottenham, Mauricio Pochettino isn't quite going that far, but has certainly borrowed from Welles' handbook. Since joining the club, the manager has kept at least one senior player on the sidelines at all times, possibly as a deliberate reminder to the rest of his squad to work hard and, in Wellesian fashion, remind everyone who is in charge.