Safety is one of the most under-appreciated positions in all of football. It is vitally important to the modern defense, yet consistently overlooked -- to the point where even TV broadcasts crop safeties out of most plays.
However, safeties are responsible for communicating the defense to, and lining up, the rest of the secondary. They are responsible for being erasers for the rest of the defense; diagnosing the offense and giving help where it’s needed or finishing off plays.
In multiple-look, blitz and man coverage, heavy defenses like the the New York Giants run, safeties are even more important.