“It's frustrating because I know we're capable of doing that. It could go to goal difference again and that's an issue.
“At the moment we're only two goals better off than Manchester City but that could be undone in one game. We've had opportunities to be better.”
Nevertheless, despite the manager’s concerns, United go into the weekend’s fixtures holding a seven-point lead at the top of the table. City host Liverpool on Sunday, meaning a Reds win at Craven Cottage on Saturday would, temporarily at least, extend the Reds’ lead into double figures.
“It's very tempting to think about being 10 points clear,” Sir Alex admitted, “but the most important thing is to keep our feet on the ground and try and win our game at Fulham. Then we'll see where that takes us.
“There's a long way to go [this season. Fourteen games. A lot can happen.
“We're not certainties. Nobody's a certainty in this league - they never have been. We were 11 points clear of Arsenal one year and lost the league. We were 12 points behind Newcastle one year and won it. It's an unremitting league. If you make mistakes you get punished.
“[That’s why] I don't think we can afford to drop any points. When you drop points it only encourages everybody around you.