 Executive producer and showrunner Phillips departed the series, after a record-setting season-four finale, to spend more time with his family; "24" co-executive producer Chip Johannessen took over Phillips' post.Head writer Melissa Rosenberg left after season four, as well.After the conclusion of season five, Chip Johannessen was revealed to be leaving the show after a single run, and Scott Buck would take over as showrunner from season six onward.