Crouch is convinced that if King can stay fit then there will be no better centre-back at the World Cup.
"Ledley is a fantastic player and if fit he would be a definite," said Crouch.
"Obviously the manager has to weigh up whether he can take him to the World Cup and if he is fit enough.
"He has played three games in nine days and I don't think he was feeling that bad. He would have more rest at the World Cup. Ledley has had a really good end to the season, he has been fantastic. When he is fit I think he has got to be one of the best centre-halves in the world.
"It is a real shame with his injury problems otherwise I think he would have gone on to be the world's best but they held him back a touch.
"I don't want to tell the manager what to do, the manager will have his own ideas, but in my opinion he is a fantastic centre-half.
"On his day, when he is fit, there is no-one better."