Rather than Patrick Dempsey, it could have been Rob Lowe who took on the role of McDreamy. In his 2014 memoir, Love Life, Lowe confessed that he'd been offered the role of Derek Shepherd on "Grey's Anatomy", but he turned it down to star in the short-lived CBS series "Dr. Vegas" instead. "Year after year after year, all of ABC's new dramas flopped," Lowe wrote in the memoir. "CBS was on a hot streak that continues to this day. AlthoughGrey'swas a much better script, I chose "Dr. Vegas". The odds were just too stacked."