He was a fringe player of Newcastle's senior side for the 2007–08 Premier League season, but showed promising signs in pre-season friendlies, including getting two assists against Hartlepool United.
In January 2008, Troisi had a two match trial with Dutch Eredivisie club, Roda JC. Roda wanted to sign him on a permanent basis, but negotiations broke down as Troisi was a product of Newcastle's youth development and still under 23 years of age, so Newcastle would have required a compensation fee.
On 6 May 2008 it was announced that Troisi would not be offered a contract with Newcastle United after the end of the 2007/8 season.
In the media his name has been mentioned for a couple of Dutch and Spanish teams, including NEC. It was stated recently a "world renowned" Spanish team is courting him. He joined Gençlerbirliği S.K. at the end of August 2008 on a three year contract. He made his debut for Gençlerbirliği S.K. on September 14, 2008 against Eskisehirspor K at the 19 Mayis Stadium in Ankara, coming on as a 65th minutes subtitute for Engin Baytar.
Troisi made his full international debut for Australia in a goalless friendly against Singapore on 22 March 2008, playing in left midfield.