Unicom, which specialises in telecoms for small business, monitored call volumes during the build-up to the match - and call levels started to tail off by as early as 10am, with a 40% reduction in the last hour of the working day compared to a normal working day.
Overall, call volumes from small businesses in Manchester were down by 12.57% for the day.
"It's rare that we see anything like that level of fall-off in calls from one day to the next, and this was one of the biggest drops offs we've seen in the Manchester area in the history of our business," said Tony Eagleton of Unicom.
"There was clearly a mass exodus from small businesses in the area from around about lunchtime, then the lines went very quiet - around half as many calls as normal - as 5pm approached.
"Interestingly, call volumes between 2am and 3am on the morning of the game were double the usual level, which we suspect was due to a number of businesses dealing with food and drink orders for later that day, and quite likely cab and minibus firms dealing with passengers for the first flights to Moscow."
"There was also a 40% increase in call volumes in the hour after the game, presumably due to United supporters wanting to share their good news."