HugoFirst
Are you
seriously trying to suggest that competence in the basic flying of the aeroplane on which you are rated constitutes complete mastery of it's overall operation ?
The basic aircraft handling side of the job is a minor component of the entire task (at least, if you're trying to do it properly, it is !). It's taken as read that anyone in either seat can at least cope with basic aircraft handling !
When a Captain becomes incapacitated, it's correct
decision making, thinking ahead, planning, communicating, monitoring etc. etc. etc. that "saves the day".
(but I always try to remember the priorities -
Aviate, Navigate, Communicate, in order of decreasing importance).