Linesman Peter Kirkup won't be axed, despite his gaffe in Chelsea's 0-0 draw with Blackburn Rovers.
But while Kirkup's blunder at Stamford Bridge was equally serious, Hackett does not accept it was obvious as it took several replays to establish Salomon Kalou was onside.
Although senior refereeing figures admitted last night that the decision was incorrect Chelsea manager Jose Mourinho's angry protest will be investigated by the FA today.
Mourinho came on to the pitch at the end to remonstrate with referee Howard Webb. Disciplinary chiefs will base their response on Webb's report of the exchange.
