I'm pretty certain 'roids aren't known for preventing hammy injuries.
Hammy injuries and Thompson's incompetence contributed primarily to Claymaker's decline in production. Can't accumulate pretty stats if you're sitting out games due to a weak hammy. And you're definitely not gonna be the elite pass rusher you were when they're playing you out of position, thanks to the GM's inability to acquire a bona fide ILB.
It's highly possible that the Claymaker never used illegal PEDs. Maybe he's just "gifted" genetically.