The 31-year-old has started just one Premier League match this season following Roberto Soldado’s arrival at White Hart Lane in the summer.
Defoe, who has been linked with a January switch to his former club West Ham, was part of England’s 2010 World Cup squad but concedes he may be overlooked by Roy Hodgson for next summer’s tournament in Brazil.
"Getting into a World Cup squad is based on merit and you have to play for your club," said Defoe. "As a forward, if you are not getting the chances, it will be difficult.
"Frank Lampard got it right when he said the other day that everyone is fighting [for places]. It's important that everyone goes back to their clubs and plays games to try to impress the manager. It's a long way to go before the World Cup. There is a lot of football to be played and we will see what happens. You never know, I might play every game from now on."