EXCLUSIVE: Bob Greenblatt departing Showtime; David Nevins expected to take over

In a case of one former Fox executive-turned-producer replacing another former Fox executive-turned-producer, David Nevins (above, right) is expected to take the top entertainment gig at Showtime -- replacing Bob Greenblatt (above, left).

No deal has been announced yet, and Nevins was said to be mulling several options (following his departure as president of Imagine TV, which was revealed today). But a deal is expected shortly, as Greenblatt is indeed stepping down as entertainment prexy after seven successful years.

Speculation about Greenblatt making the decision to move on has been rampant for weeks.

Greenblatt's exit is coming entirely of his decision as his most recent contract is set to expire next month. Exec has had a stellar run of developing signature skeins that have transformed the pay cabler, including "Dexter," 'Weeds," "Nurse Jackie," "The L Word," "Californication" and "The Tudors."

A rep for Showtime declined comment, as did Nevins.