The British actor, who is known for starring in Buffy The Vampire Slayer, will replace Pierce as centaur Chiron in Percy Jackson And The Olympians: The Sea Of Monsters, according to The Hollywood Reporter's Heat Vision blog.
There's no word on why the former James Bond won't be returning to the role he portrayed in 2010's Percy Jackson And The Olympians: The Lightning Thief.
It isn't the first news of changes for the series, as it was recently reported that Castle star Nathan Fillion will take over from Dylan Neal as Hermes.
However, several of the original film's stars will be reprising their roles, including Logan Lerman as Percy Jackson, Alexandra Daddario as Annabeth and Brandon T Jackson as Grover Underwood.
The sequel is due to be released in March 2013.