Steve Bruce knows the walk. For the best part of a decade, the route out onto the pitch at St Andrews had the comfort of a warm bath. On Sunday, he knows it will feel more like he has been dropped through ice.
Bruce has been back to his old stomping ground as a visiting boss with Sunderland and Hull but he knows this time, with rivals Aston Villa, the walk will feel longer. Much longer.
"I've got nothing but respect for the club and the people who support it, but I'm now enemy number one," Bruce, who spent two years with Blues as a player and six as a manager, winning two promotions to the Premier League, told BBC WM 95.