Police leave has been cancelled across the West Midlands as forces brace themselves for potential FA Cup disorder as Cardiff, Manchester United and Millwall fans take on Midlands teams tomorrow.
Cardiff travel to Staffordshire to play non-league Chasetown, who beat Port Vale 1-0 to go through to the third round of the competition.
Milwall fans will be making their way to the Bescot Stadium to play Walsall, while Manchester United supporters will take on Aston Villa.
All three kick-offs have been staggered to help prevent any possible confrontations between rival fans.
British Transport Police, who will have about 100 officers patrolling Birmingham New Street station, have cancelled all rest days tomorrow.
PC Jim Rentell, their football intelligence coordinator, said about 100 officers would be patrolling New Street station from 11am to 11pm.
"Cardiff fans are the least of our worries because there's only 500 or so of them going to Chasetown, by coach, as the ground's quite a way from the nearest station," said PC Rentell.
"Villa and Manchester United is a different kettle of fish altogether, as the visitors have got 15 per cent of the ground and they will be coming from all parts of the UK, and, as such, New Street will be the focal point.
"Walsall kick off against Millwall at 2pm but the game at Villa Park doesn't start until 5pm, so we will be trying to keep them from meeting in between those matches.
"All rest days have been cancelled for BTP officers across the region, and I believe West Midlands Police are doing something similar."
PC Rentell added: "If anyone steps out of line they will cop it. However, we've had no intelligence suggesting there will be any major problems."
Staffordshire Police have also cancelled leave for some officers, as 2,000 fans are expected to descend on the Scholars' ground at Church Street for 1pm kick-off.
Chief Supt Mick Harrison, the policing commander for the event, explained Staffordshire had worked closely with both clubs and South Wales Police to come up with a suitable strategy.
He said: "We've got enough officers to police this match safely, however some rest days have been cancelled on Saturday, for example those who have public order training, but we have to have officers to police other parts of Staffordshire as well on that day.
"I want to take the issue of hooliganism out of this day, because this is a momentous day for ChaseTown and their supporters. "I just hope the best team wins on the day."
This FA Cup tie is ticket-only and Church Street itself will be closed between 8am and 4pm to everyone apart from local residents..
"Extra officers will be on duty in the area, to try to keep any disruption to a minimum."