Chelsea had few complaints about Branislav Ivanovic's red card for fouling Ashley Young as he raced through, but the dismissal of Fernando Torres for diving was bitterly disputed by the home side - and they looked to have a case.
The Spaniard appeared to be caught by Reds defender Jonny Evans but referee Mark Clattenburg ruled he had dived and produced a second yellow card, to the obvious astonishment of Torres and the undisguised fury of Chelsea.
Substitute Hernandez then smuggled in a winner from close range but it was converted from an offside position to leave Chelsea manager Roberto Di Matteo nursing a burning sense of injustice.