The Manchester United Supporters' Trust says the decision to reduce the away allocation at short notice is a disgrace.
The match will start at 17:30 on Saturday, according to the league.
The allocation of United's away tickets has been reduced due to police concerns.
The Metropolitan Police are being considered for legal action by Must.
The Met said that because TV commitments prevented the "high-risk" fixture from starting by 16:45 on the rearranged date, an alternative solution had to be reached.
The safety of fans and those who live and work in the community is the Met Police's first priority.
We have to balance this commitment against our other police responsibilities in London.
It was not the only option for the clubs and was not taken directly by the police.
United have already sold their initial away allocation of 2,994, and the club is considering options as it tries to remove 622 sold tickets.
The statement said: "We are considering legal action against the Met Police on behalf of our fans affected by this decision to reduce our allocation, after tickets have been sold to fans in good faith."
A match reaching a point a few weeks before being played without a confirmed time is a terrible precedent.
It's a disgrace that an away allocation has been cut weeks before a game.
The match was moved to the Saturday because of the next day's game.
The kick-off time has been decided 15 days before the game after extensive talks between both clubs and the police.
While we are very disappointed by the outcome, it is clear that it is a final decision.
The police have insisted on a reduction. We were able to increase the allocation to 2,370.
Must urged the league to look at policing, away allocations and late decision-making.
"This fixture has been a shambles by the authorities collectively, and regardless of any buck passing, as usual it's fans left as the loser from it all."
The trust stood by the decision and criticized it.
The kick-off was announced with less than a week's notice. The confirmation is that supporters are disposable as long as the game is broadcasted.
This is an insult and a danger. The Manchester United Supporters' Trust and the 622 fans who will have their tickets canceled are with us.