As a junior from Nhill, McCartney had a huge reputation and there was tremendous controversy even before he was drafted as he told some clubs he would not play with them if they chose him. Collingwood chose him but he had trouble living up to the expectations as a key defender or forward.

After four years at Victoria Park he went to Adelaide and in 1995 he had a good year appearing in 20 games. Others leapfrogged him in the next two years and after playing just six games in 1997 he crossed to North Melbourne for 1998. McCartney lacked pace off the mark, but he quickly re-established himself at AFL level after crossing to Arden Street. He quickly asserted himself as the regular Roo centre half-back, but missed the 1999 premiership side through suspension after striking Brisbane's Clark Keating in the Preliminary Final. In succeeding years he was a pillar of strength in defence. McCartney became a national hero when he helped fellow Australians immediately after the Bali Bombings late in 2002. Although badly burned and hospitalised, he eventually returned to full training wearing protective bandages. He won back his senior place 11 rounds into the season and in an emotional game contributed to a win over Richmond. At the end of the match he announced his retirement, saying that he had achieved all he could and had realised when sidelined with an injury a few weeks earlier how good his body felt during the rest. In retirement, he joined the Western Bulldogs as the club's List Manager.