Crouch believes his fellow Tottenham star is well worth a place on the plane to South Africa next month.
He said: "I've known Ledley for a lot of years and I know what a superb player he is.
"As long as he can prove his fitness, he will be up there as one of the best centre-halves at the World Cup."
Crouch first played with King as a schoolboy at Spurs before the pair were reunited last summer, helping the north London club finish fourth in the Premier League this season.
And the 6ft 7ins forward has seen first-hand at White Hart Lane how talented King is, despite the defender being unable to train between matches.
He said: "I've known Ledley since I was 13 in my first spell at Spurs. He was fantastic even then. You knew he was going to be world class and he has proven that.
"He has proved his quality this season, hopefully he has proved his fitness.
"Ledley has to be managed a bit different to the rest of the players. He has to do his own thing and train when he feels capable of it."