Thornton staked a major claim for inclusion in Greater Western Sydney's side after booting eight goals in the Giants reserves' 10-point NEAFL win over Belconnen on Sunday.

Recruited by the Giants through the pre-season draft when delisted by the Blues, the 188-game veteran's bag will boost his chances of playing his first AFL game for his new club.

An opportunity is there for the taking up forward after gun youngster Jonathon Patton's season-ending knee injury in the Giants' 72-point loss to St Kilda at Manuka Oval last week.

Sunday's match developed into a high-scoring shootout in the second half, and Thornton's influence proved the difference in University of Western Sydney's 20.17 (137) to 19.13 (127) victory.

The 29-year-old had missed the past two games through suspension, after playing in defence in round one.

But he admitted he would prefer to play in the attacking 50 in the twilight years of his career.

''The last couple of years at Carlton I was playing up forward, I probably enjoy playing up there more these days,'' Thornton said.

''I don't have the pace I used to, and I can read the ball a bit better.''

Thornton believes his experience could be a handy foil for Jeremy Cameron, who is desperate for another key forward to take the pressure off him after Patton's injury.

''I think that's probably half the reason why I've gone forward as well, whenever an opportunity comes up I want to take it,'' he said.

Thornton's former Carlton teammate Setanta O'hAilpin kicked five goals in his second game for the Giants on Sunday in a 41-point loss to Melbourne.

Both sides kicked only six goals each in the first half, but the Giants took a 16-point lead at three quarter time after a thrilling 10-goals-to-eight third term.

Momentum changed hands several times in the final quarter, but a late snap from University of Western Sydney's Nathan Wilson thwarted the host's challenge.

Belconnen coach Matthew Lokan said the Giants midfield allowed Thornton to inflict damage on the scoreboard.

''I actually thought our guys did an OK job on Bret, they're just very hard to stop when they run and carry and break lines,'' he said.

The Magpies expect Mulrooney medallist Shane Harris to return from a knee injury in a few weeks.