The Irish Football Association (IFA) is understood to be shocked by a PSNI decision not to provide an escort for the coaches of both teams to last night's Euro 2020 qualifier at Windsor Park.
It is the first time police have not been made available to ensure both teams have safe passage to an international match at the national stadium.
A capacity crowd watched as Northern Ireland defeat Estonia in the first match of their qualifying campaign.
The Northern Ireland team made the journey across Belfast from the Culloden Hotel, while the Estonian team travelled to the south Belfast venue from the Stormont Hotel, meaning both had to pass through the centre of Belfast during rush hour.
An IFA source claimed it was the short notice of the PSNI decision that caused the major headache, because the IFA was given no time to put alternative measures in place.
In the match meeting, the Estonians said that they could not change their match-day itinerary, which had been set weeks before on the understanding that the team would have an incident-free passage to the venue.
An IFA source said the last-minute decision by the PSNI had left it in a difficult position.
"On Wednesday night the PSNI confirmed that they would not be providing police escorts to either Northern Ireland or Estonia to tonight's Uefa Euro 2020 qualifying match at the National Football Stadium at Windsor Park," the source said.
"This is the first time that police escorts have not been provided to a senior international football match in Belfast.
"While we fully understand the pressures that the PSNI are under and hugely grateful for the service that officers provide, the short notice meant that no contingencies could be put in place.
"We were left with the possibility that the teams would be delayed getting to the match, that there could have been a delay in opening the gates to spectators and possibly even a delay to kick-off."
The PSNI said it had carried out a risk assessment ahead of the fixture, which attracted almost 20,000 spectators to the south Belfast stadium.
Before the game, Chief Superintendent Jonathan Roberts said: "When planning operations to support significant public, cultural and sporting events, police carry out a comprehensive risk assessment to inform our operational decisions.
"As a result, an operational decision was taken not to provide team buses with a police escort for tonight's match.
"With over 18,000 football supporters attending the match at the National Stadium, this football match will be policed in a manner and style appropriate and proportionate to the threat and risk presented.
"The policing operation for the match saw police officers deployed around the stadium performing public safety roles."
The match kicked off at the expected time of 7.45pm.
Any delay in the start of the game would have exposed the IFA to sanctions from European football's governing body, Uefa, and the problem could have been compounded as a road accident on the Sydenham Road at around 5pm yesterday saw the road closed in both directions, causing knock-on delays on the Sydenham Bypass, M3 and Airport Road.
In last season's Champions League, Manchester United were hit by a €15,000 (£12,966) fine after arriving late for a group match against Valencia due to traffic congestion around their Old Trafford ground, which delayed the kick-off by five minutes.
Uefa fined Arsenal the same amount for a late kick-off in their Europa League game against Qarabag in London last December.