Though Paul Bettany was originally slated to lead the 1960′s set series Masters of Sex, the actor has since fallen away from the project. But now Michael Sheen (Frost/Nixon) has stepped up to the plate to play the human sexuality pioneer William Masters. In addition, he will be joined by Lizzy Caplan (Party Down) playing his better half Virginia Johnson, a more dramatic role for the actress. Michelle Ashford (The Pacific) has written the series based on Thomas Maier’s book Masters of Sex: The Life And Times Of William Masters And Virginia Johnson, The Couple Who Taught America How To Love which chronicles the lives, romance and pop culture trajectory of Masters and Johnson, whose research touched off the sexual revolution. Shakespeare in Love director John Madden will be at the helm of at least the pilot which begins production next month. Bettany is a great actor, but I’m interested in seeing Sheen taking a big lead series role like this too. Hit the jump to read the full press release.