Joe Hart has admitted that he cannot afford to let his form drop due to the competition for places in the England squad.
The Manchester City goalkeeper is considered to be holding the number one shirt in safe hands, but he believes that the quality of Ben Foster and Fraser Forster means that he must guard against complacency.
"I've got to be at my best, I've got to be working hard and you've got to stay level-headed otherwise it can go wrong," Hart told reporters.
"Ben is a fantastic goalkeeper and we're really lucky that, as a unit, we've got a lot of respect for each other on and off the field.
"He has been absolutely fantastic since he's come back in, a real breath of fresh air, and the same goes for Frase as well. We work well as a group. We get the best out of each other and want the best for each other."
England start their World Cup campaign against Italy in Manaus on Saturday night.
