Defoe seems certain to begin the new season playing second fiddle to coach Martin Jol's preferred strike pairing of Darren Bent and Dimitar Berbatov.
England star Defoe failed to secure a regular first team place last season - scoring just 10 league goals. But despite rumours that he would be leaving White Hart Lane this summer, Defoe is ready to battle it out with Robbie Keane, Berbatov and new signing Bent.
But the striker has two years left on his contract with the north London club and Ferdinand reckons the time for him to contemplate his next move could come as early as next January.
Ferdinand said: "Tottenham have got the best quartet of strikers in the Premiership at this moment in time.
"The only way you can keep them happy is by playing them. I don't think the manager has a rotational policy, he takes it game by game. If a player is scoring then he is in.
"I was very fortunate in my career because there wasn't many occasions when I was left on the bench. As I got older it happened of course but not in my heyday. Whenever I was dropped I never knocked on the manager's door, I always looked at my own performance.
"Jermain has got to do the same and that's what he says he wants to do. A lot of players would have seen Darren Bent come in and said 'right, I'm going' but Jermain has not done that.
"He believes in his own ability and if he gets the opportunity he will stay in the side. But six months down the line is another time for Jermain to assess his situation and for Tottenham to do the same.
"Because if he is not in the side, Tottenham will not want it to get to a situation similar to what happened with Sol Campbell, where he gets into the last year of his contract. I think they will say either Jermain Defoe is up for sale or he is not.
"If he's in the side he won't be for sale and they will be looking for him to sign a new contract. If he is out of the side they will be looking to sell him. Crunch time for Jermain will come in January."
But Ferdinand is full of praise for Tottenham's acquisition of Bent who, he says, offers the side something different to Defoe.
Ferdinand added: "He's a good signing. He's proved he can score goals in the Premier League.
"He was out of action for a little while last season but still came back and scored goals. He is a proven goalscorer in the Premiership.
"He is someone who plays off the service he gets, he is not like a Jermain Defoe who can pick the ball up, beat two players and smash it in the back of the net.
"He reminds me of myself a little bit because he plays on the last shoulder and wants to get into the box and score his goals there. He's a good acquisition for Spurs."