Manchester United manager Sir Alex Ferguson has warned Rio Ferdinand and Nemanja Vidic that they have no guarantee of a first-team place when they return from injury.
United's usual first-choice central defensive pairing missed Monday's 3-0 win over Spurs with leg and calf injuries respectively.
New signing Phil Jones as well as Jonny Evans and Chris Smalling stepped up in their absence, keeping a clean sheet in United's 3-0 victory at Old Trafford.
Serbian stopper Vidic is still three weeks away from a return but Ferdinand is set to be fit for United's home clash with Arsenal at the weekend.
However, Red Devils boss Ferguson revealed the duo may not get back into the side after admitting their young understudies' performances had left him with a selection dilemma.
"Rio and Nemanja are aware of the abilities of the young players, there is no question about that," said the Scot.
"When they are both fit, or one of them is, I will have a decision to make"