Watched it again also and Vertogeen attacked the ball with huge momentum from behind in the middle of 2 defenders with Carra missing it (or could not jump high enough). GJ I think thought that Carra would head it, but, who do you want to replace him with? We cannot but 11 players, the priority is central defence.
Just watched it another time too, and the problem with Johnno in that situation was that he was ball watching - as you say probably thought Carra would deal with the situation.
I'm not asking for Johnno's replacement but for him to learn from his mistake and move on. Next problem. Fix. Move on. Next problem, and so on.
As it is now he is constantly caught ball watching in defense. He's actually a bit like Assou-Ekotto: Lazy in defence but likes going forward!