Sir Alex Ferguson believes Manchester City should worry if Manchester United are still top of the Premier League on New Year's Day.
United have three games to preserve their present six-point advantage but Ferguson is convinced if his side achieve their objective, it will take something special to deny them a record 20th league title.
"I look at December as an opportunity to gather points," said Ferguson.
"If we are top of the league on New Year's Day we know fine well, and so does everyone else, that we are going to be in the ball park at the end of the season."
A week after United beat City at the Etihad Stadium, Roberto Mancini's men served notice they are not going away with their best performance of the season at Newcastle.
While Ferguson thinks his players should take note, he is expecting a tough challenge for the title from City.
"It was a wake-up call for us," said the Red Devils chief.
"City and ourselves will be battling it out and they played really well for the first 20 minutes.
"But we expect a challenge. It is what we are good at."
With the busy festive period looming with five fixtures in 22 days Ferguson is delighted to have only Rafael, Nani and Shinji Kagawa on the sidelines after a glut of injuries this season.
And he is particularly pleased that skipper Nemanja Vidic is back in the fold after virtually a year on the sidelines.
"Nemanja is one of the best, a penalty box defender, there is no doubt about that," added Ferguson.
"People have spoken about us losing goals. I would hope that stops, or reduces it a good bit anyway."