Concerns were raised about the timing of the match as heavy drinking and trouble between fans may ensue thereafter.
A secondary reason was due to the sheer volume of fans being present in the area- with Bolton playing Stoke the following day at Wembley in the other semi-final and Liverpool travelling to the Emirates to face Arsenal all during the same weekend.
A Met spokesperson said according to the Guardian: "We deal a lot of big events in the capital and we will, as always, have the appropriate measures in place. The game between the Manchester clubs is no different to any other large occasion we would police."
With an estimated 100,000 fans travelling from the north-west and therefore a perceived problem for the BTP, the FA say migration troubles would be an issue at whatever time of the day.
"There would have been implications for arrival and dispersal even if the match had been staged at eight in the morning," a spokesperson said.
"5.15pm is deemed to be an optimum time with regard to the TV audience and this was the choice of ITV, which as the main broadcaster, could state a preference."