It will be United's first game back in the division following relegation from the Championship, and could not have asked for a much harder test than a game against the title favourites.
McAllister expects a tough game from the Iron, with the home players keen to prove they can challenge for promotion back to the second tier of English football.
"Scunthorpe should be a good game to start with," he said.
"They played Championship football last season, and obviously suffered relegation. But they will be a tough competitive side who will want to do well.
"The new teams in this division are predominantly footballing teams which should make for some good games.