"He just hasn't been able to get a clean run at it," Hawks football manager Mark Evans said yesterday.
Thorp, called up early this season to play a back-up ruck role, developed soreness after returning to play for Box Hill in the VFL.
"It started to become painful during and after games," Evans said.
"It doesn't look like a new injury. We think it might have been there for a while, but for the last couple of years it hasn't been an issue."
Thorp faces an uphill battle to maintain a stranglehold on a spot on Hawthorn's list. But Evans said the club was in no mood to give up on Thorp, who played only one game this year for four disposals.
Entering 2009 he had played only one game -- an impressive debut in 2007.
Groin injuries have been the biggest issue for Thorp, a 20-year-old who stands 194cm and weighs 88kg.
"Look, he can play footy. He is a strong mark and a good kick," Evans said. "We will give him a chance to get over this and prove himself."
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