He made his senior debut for London Irish against London Wasps in 2009 and made a total of 78 appearances in his 4 years playing for the Exiles. During this time he gained a reputation for strong scrummaging and a physically imposing style of play.[3][4]
It was announced that he would leave Irish at the end of the 2012–13 season and link up with the Melbourne Rebels ahead of their 2014 Super Rugby campaign. He also spent a season playing ITM Cup rugby in New Zealand for the Hawke's Bay Magpies.[5][6]
Lahiff qualifies to play international rugby for Australia through his father.[7][8]
On 30 January 2015, Bath Rugby confirmed the signing of Lahiff with immediate effect.[9] Rejoining Toby Booth and Neal Hatley, who were coaches at London Irish during his spell there, Lahiff was named in the squad to play Harlequins in the LV= Cup the next day.[10]
Lahiff signed for French Top 14 side Clermont as cover during the 2019 Rugby World Cup, but the deal was called off due to a medical issue.[11] Lahiff joined Bristol Bears on a one-year contract for the 2019-20 season which has since been extended.[12]