
23. William Gallas
In 2010, Arsenal offered Gallas a two-year extension to his deal. However, the French international snubbed their deal because they didn’t offer him a wage increase. This shocked the club because they broke their standard one-deal extension policy for over-30 players. Gallas didn’t appreciate this and rejected it. Eventually, he departed and joined their rivals, the Spurs.

This was remarkable because these teams are intense rivals. Meanwhile, Gallas was the club captain at the time. After one of the team’s biggest contract holdouts, he left under a cloud. Gallas broke all of the bridges with the club and the fans hated him. It didn’t matter that he served them faithfully before this. He broke an unwritten rule that no player should ever do (via The Mirror).