'Green Lantern' director Ryan Reynolds didn't want any other person to play the lead role, even though he auditioned other actors.
The director knew he wanted to work with the Canadian actor straight away because he is "physically terrific" and knew the role.
Martin said: "I wanted Ryan Reynolds from the start. It was largely because of his ability as an actor.
"He looks great and he has a sense of humour. He is physically terrific. I mean, what more could you have? He's got all of those elements.
Martin auditioned less than 10 people for the iconic role, but found Ryan was the only man for the task.
He added: "I think we tested something like 8 or 6 people. I can't quite remember the number. As for them being in the film, you go through a process of elimination. You look and say, 'Well .' and to be honest, Ryan was always my first choice. You go through a studio process where you obviously look for and test out other people. If for no other reason, for you to confirm who you first thought was the great person.
"And for my money, it was always Ryan. I thank God that has turned out to be true."