Originally from Sydney in New South Wales, Hayes was recruited from the Pennant Hills Demons AFC by St Kilda in the 1998 AFL Draft. He is a highly-skilled, classy midfielder. Hayes was captain for the 2004 season, as part of St Kilda's policy of rotating the captaincy to a different player each season.
His honours include All-Australian selection in 2003, the same year he took out the Trevor Barker Award for the Saints' Best and Fairest player. He also won All-Australian selection in 2005, as one of the senior members of the Saints' midfield.
After a strong start to season 2006, Hayes ruptured his anterior cruciate ligament against the Kangaroos in round 9, requiring a minor knee reconstruction which sidelined him until the 2007 season. In just his 5th game back in the 2007 season, he suffered a broken collarbone, sidelining him for 3 weeks, although he managed to come back and play 19 games for the year.
Hayes was a Co-Captain and part of the Saints' 2007 leadership group - dubbed the "Young Saints", which also included Justin Koschitzke, Luke Ball (Co-Captain) and Nick Riewoldt (Co-Captain). Also included in the leadership group were Aaron Hamill, Fraser Gehrig, Nick Dal Santo and Robert Harvey.