[2][3][4] In Round 15 of the 1996 ARL season, Cowboys' head coach Graham Lowe named Hannay to make his first grade debut against the Western Suburbs Magpies.
The selection was ultimately blocked by the Australian Rugby League (ARL), as Hannay (who was born in 1980), had to turn 17 the year he debuted to be eligible.
[citation needed] In 2003, Hannay enjoyed a breakout season, playing 23 games and scoring 230 points, second in the NRL only to Hazem El Masri's 294.
On 16 July 2003, he made his State of Origin debut for Queensland, starting at centre and kicking four goals in a 36–6 Game III win over New South Wales at Suncorp Stadium.
[7] In Round 23 of the 2003 season, Hannay set the record for most points (24) and most goals (10) in a single game for the Cowboys in their 60–8 win over the South Sydney Rabbitohs.
[9] Despite this, Hannay earned a recall to the Queensland side, starting at centre in their series-deciding 16–14 win over New South Wales at the Telstra Dome in Melbourne.
In June 2007, he was dropped from the Sharks' NSW Cup side and began playing for the Gymea Gorillas in the local Cronulla-Sutherland District competition before being granted a release by the club.
Hannay did not get to finish the season, as he, along with Australian teammates Jace Van Dijk, Tony Duggan, Damien Quin, Darren Mapp and Mark Dalle Cort were deported after the UK Border Agency ruled they breached visa regulations.
[26][27] On 20 July 2020, Hannay was named as the interim head coach of the North Queensland Cowboys following the resignation of Paul Green.
[29] On 22 September 2020, after being overlooked as full-time head coach of the Cowboys, Hannay announced he would leave the club, despite being under contract for the 2021 season.