Sir Alex Ferguson has insisted that Rio Ferdinand and Nemanja Vidic are fully aware of the threat to their Manchester United places posed by the three young defenders he has introduced to the team this season.
Ferdinand and Vidic are both in contention for Saturday's clash with fierce rivals Liverpool, leaving Ferguson with a major selection dilemma at centre-back.
What was once an automatic decision is now anything but, with Phil Jones, Chris Smalling and Jonny Evans all pressing their claims for a starting berth.
"Rio and Nemanja are well aware they are going to have to play well to keep their places," said Ferguson.
"Competition is so fierce now with these young lads coming through."
Back to form
For Ferdinand, there is the added complication of his place in Fabio Capello's Euro 2012 squad being in doubt.
His failure to oust Jones and Evans from the team that faced Norwich looked to be central to Capello's thinking when he was omitted from the squad to face Montenegro last week.
Ferdinand still wants to represent his country, but Ferguson concedes Capello might well be looking at an alternative strategy now.
"Rio is back to his best form," said the Scot.
"He has trained really well and his experience will be vital.
"The England thing is unfortunate because he missed a couple of appearances through injury and maybe Fabio is looking to the future.
"Some managers think that way. There is nothing wrong that."