In a surprise move, X-Men: First Class director Matthew Vaughn has elected not to helm the upcoming sequel, X-Men: Days of Future Past. Deadline is reporting that, among those being considered to replace him, is X-Men and X2's Bryan Singer, who also produced Vaughn's 2011 film.

Scheduled for release on July 18, 2014, X-Men: Days of Future Past boasts a script by Simon Kinberg and is said to be inspired Chris Claremont and John Byrne's comic book storyline that ran in Uncanny X-Men #141 and 142 back in 1981. "Days of Future Past" introduced the idea of an alternate future for Marvel's mutants that grew out of the Brotherhood of Evil Mutants killing an important senator, leading to a future where all mutants are hunted by Sentinels.

Vaughn is rumored to instead move forward with his proposed feature film, The Secret Service, an original property that re-teams him with Kick-Ass creator Mark Millar. He will still maintain a creative connection, however, to X-Men: Days of Future Past, remaining aboard as a producer.

The news comes on the heels of this morning's reveal that the studio's upcoming The Wolverine will not be a prequel as originally suggested but will, instead, take place after Brett Ratner's X-Men: The Last Stand.