Boak was selected with Port Adelaide's first selection and fifth overall in the 2006 AFL draft from the Geelong Falcons in the TAC Cup. He made his AFL debut in a 31-point victory in round 12 of the 2007 season against Essendon. Boak continued to rise since his debut, accumulating 23 possessions against the Western Bulldogs in only his third match. The following week, against Richmond, Boak kicked his first ever AFL goal. In round 19 against Carlton, he earned a NAB Rising Star nomination for his 28 possessions and 2 goals. Boak's went on to play in the Port Adelaide team which competed in the 2007 AFL Grand Final against Geelong, losing by a record margin. At the start of 2008, Boak picked up where he left off, playing a greater role in the Port Adelaide midfield alongside senior players such as Domenic Cassisi, Kane Cornes and Shaun Burgoyne. He played in 17 games and averaged 20.1 disposals. Boak continued to improve in 2009 winning the Gavin Wanganeen Medal and averaging 23.7 disposals for the season.