 Robertson made his first team debut for Sheffield United in September 2008, as a second-half substitute during a 6–0 defeat against Arsenal in the third round of the League Cup.After the club's exit from the League Cup, Robertson joined Championship club Southampton on a three-month loan deal with Southampton winger Nathan Dyer heading in the opposite direction.Robertson scored his first goal for Southampton against Norwich City, a strike from the corner of the box that curled into the top corner.