Not only was best mate and Wollongong FC keeper Justin Pasfield also left out, but Timpano would have been a certain starter if not for his horrible run with injuries.

Pasfield was a member of the Australian under 23 side that took part in a pre-Olympic camp - including a start against the Chilean under 23s - but was overlooked in favour of Shoalhaven junior Adam Federici and Perth Glory stopper Tando Velaphi.

Ex-Sydney FC player and Bulli junior Ruben Zadkovich was also named in Graham Arnold's squad.

Timpano was Olyroos skipper when the side began its qualifying odyssey, but has battled groin, foot and hernia injuries since.

The 22-year-old captained Australia at Joeys (under 17s) and Young Socceroos (under 20 level) - his next major goal was to play at the Olympic Games.

He admitted he'll have mixed feelings watching the Olyroos tackle defending champions Argentina, Serbia and Ivory Coast in China next month.

"It is disappointing and it will be hard watching the boys while they're there, but I'm just looking forward to having a good season with Sydney now," Timpano said.

Timpano is on the comeback trail after two seasons in the wilderness and hopes to cement a spot in John Kosmina's starting side for the upcoming A-League season.

He played a full game in Sydney FC's trial match against NSW Premier League side Blacktown City and grabbed a goal in Sydney's 2-1 loss to Sutherland on Thursday.

"I've played a few minutes here and there, but hadn't got through a game comfortably until last week when I pulled up pretty well," Timpano said.