Fergie branded the tackle as "shocking", and to make matters worse, the referee booked Cole but failed to award United a penalty.
Hernandez was replaced by Dimitar Berbatov for the last quarter of the match that Ferguson's side won 3-1.
The United boss told MUTV: "It was a shocking tackle.
"The referee booked him, so I don't understand why he hasn't given a penalty.
"Ashley Cole is very reckless at times. He is committed of course but being committed you can sometimes go over the edge a bit.
"That was an example of that."