 Season five introduced actor Kevin McKidd ( Dr. Owen Hunt ) , who was signed as a series regular after originally being cast for a specific story arc . In addition , Jessica Capshaw ( Dr. Arizona Robbins ) was originally introduced for a three episode arc , but received a contract extension until the end of the season and then became a series regular in the sixth season . Knight departed the show at the conclusion of season five , citing an unhappiness with the development and lack of screen time for his character . Directly following Knight 's departure , it was reported by Entertainment Weekly that Heigl had not returned to the set as scheduled after her maternity leave , and it was later confirmed that Heigl would not return to the show at all . 
