While in his final season at Canberra, Backo was first selected to play State of Origin football for the Queensland Maroons in the 1988 series. He played in all three games at prop forward, scoring one try in game II and two tries in game III. Queensland won the series in a three-game whitewash. In games II and III Backo won consecutive man-of-the-match awards, one of only a handful of players to do so. During the 1988 Great Britain Lions tour Backo was selected to make his test match debut at prop forward in the first of the Ashes series against Great Britain in Sydney, scoring a try. He went on to become the first Australian forward to score tries in all three Tests of an Ashes series, and at the time he was only the second Australian player to do so after legendary winger Ken Irvine. At the end of the 1988 NSWRL season Backo was the Dally M front rower of the year. A late season injury playing for Canberra saw him miss selection in Australia's World Cup Final winning team.[citation needed]
Backo's final two seasons of top-level football, 1989 and 1990, were spent in Queensland, with the Brisbane Broncos. He was selected to go on the 1989 Kangaroo Tour of New Zealand. Backo also played in a further four games for the Maroons – games II and III of the 1989 State of Origin series, and games II and III of the 1990 series – despite his knee problems,[4] which limited his participation with his club to only five appearances during 1990 and eventually forced his retirement at the end of the season. Although selected for the 1990 Australia team to play France in the NSW country town of Parkes, he was forced to withdraw because of his ongoing knee injury. In total, Backo played in six Tests and scored three tries. In 1991, Backo made a short-lived return to football to play for Logan Scorpions in the Brisbane competition.
Post playing
Backo was awarded the Australian Sports Medal in 2000 for his contribution to Australia's standing in rugby league.[5] The Indigenous Team of the Century was announced in 2001 with Backo included in the starting line-up which also included Arthur Beetson, Gorden Tallis and John Ferguson.[6] In 2004, Backo was named in the Canberra Raiders' All Indigenous team.[7]
On 2 April 2023, it was reported that Backo had suffered a heart attack the previous day and was in a critical condition in a Cairns hospital.[8] Rugby league identities Wally Lewis, Trevor Gillmeister, Steve Renouf and Darryl Brohman were among those who offered support to Backo and his family upon learning the news.[8][9]