St George Illawarra are in disarray ahead of Friday night's NRL season opener against Parramatta with Matt Cooper a definite non-starter and skipper Ben Hornby in doubt.

Cooper aggravated a hamstring injury as he attempted to prove his fitness for the Parramatta Stadium blockbuster while Hornby also failed to take part in the team's final training run in Wollongong on Thursday.

"Benny Hornby's just had to sit out, he's got an infected wisdom tooth, they're pretty painful," lock Dean Young said.

"We're confident he'll play."

The potential double blow forced coach Wayne Bennett to undertake some major reshuffling of his squad, with starting prop Matt Prior running in the centres in place of Cooper and hooker Nathan Fien deputising at halfback for Hornby.

Former Bronco Nick Emmett is set to come onto the bench, while veteran rake Luke Priddis will start at hooker if Hornby fails to overcome his illness.

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