The "Sons of Anarchy" star says he dropped out of his role due to his busy TV schedule, though a source said he actually dropped the role because he was afraid of getting stuck with similar roles.
"He dropped out of the project because he didn't want to be typecast," a source told People magazine.
"He didn't want the Robert Pattinson-esque attention that would come along with taking on this role."
2 sources now say Hunnam got cold feet on #50Shades movie, TV schedule said to have had nothing to do with his exit.— Matthew Belloni (@THRMattBelloni) October 12, 2013
"What he was taking on with this role was not what Charlie wants in his future career," another source said.
"The attention and the pressure was intense. More than anything, he hates attention, and being in 'Fifty Shades of Grey' would force him to do lots of media. ... Charlie doesn't want to be massively famous."
Rumored frontrunners to take Hunnam's place are British actor Jamie Dornan, along with previous frontrunners Alexander Skarsgard of "True Blood" and "Romeo and Juliet" actor Christian Cooke.
"Divergent" star Theo James and "I Am Number Four" actor Alex Pettyfer have also been named as potential Greys.