sparkync:
From the '11 NEC:
"(C) Cables Through Spaces Behind Panels Designed to
Allow Access. Cables or raceway-type wiring methods, installed behind panels designed to allow access, shall be
supported according to their applicable articles. '
That said, there is nothing within Art 334 that says you have to drill.
However, your local AHJ may have another opinion. The "physical damage" can be subjective.
