The young heartthrob, whose 6 million pound deal with Disney is almost twice the amount for High School Musical 3, was reportedly chosen a year ago while the original Captain Jack Sparrow was still pondering to do the film's sequel.
"Zac was extremely interested," the Sun quoted an insider as saying. "But Disney realised they couldn't make the fourth Pirates movie without Johnny. They had to offer him a small fortune to do it," the insider added.
The deal also allows the actor to star in his signature character of a basketball hero, Troy Bolton, again in High School Musical 4 while he prepares himself to share the screen with Depp.