The Red Devils returned to Premier League action for the first time in 16 days after their previous two games against Brentford and Brighton and Hove Albion were postponed.
Ralph Rangnick's side required Edinson Cavani to come off the bench to rescue a point at Saint James' Park after Allan Saint Maximin had given the hosts an early first half lead.
United's performance did not please their manager, who voiced his discontent after the game and their skipper echoed his manager's thoughts.
Maguire told the club's official website after the game: "No 16-day break in the middle of a football season is going to help you.
"The training ground has been shut, and half the lads playing are recovering from the virus so of course it's not going to help us.
"We've had people with symptoms, people without symptoms, it's been a real mixed bag for everyone at the football club and it's been a tough time.
"But you can't make excuses for sloppy passes and the opportunities that we had, especially in the first half.
"We've got to stay on the ball, we've got to stay active and we've got to play the ball in their half and we didn't manage to do that.
"You can look at that and ask whether the last 16 days had a big impact on that because it looked like we ran out of steam out there.
"A point in the end is a fair result, but it's a result that we're disappointed with."
