sentences:  In the 2011–12 season, Brisbane Roar became the first team to win back-to-back A-League championships and Postecoglou became the most successful Australian domestic football (soccer) coach, with four national titles.On 24 April 2012, Postecoglou announced his resignation as head coach of Brisbane Roar.Postecoglou left the Roar after two-and-a-half years, during which he led the club to back-to-back A-League championships, a premiership and consecutive qualification for the AFC Champions League.