Nah, it just means that he'll likely play at a reduced level of what you visibly see in his player attributes.
For example, if he's got Proficient passing under normal circumstances, coming off injury he'll still have Proficient passing but because he's been off the court for so long, his passing might be at a reduced Proficient level.
At least, that is as simple as I can make it. There's very likely more to it but just understand that he's rusty coming off injury so he'll need to either be worked back into the lineup slowly depending on your roster depth, or if he's your only chance at being successful in his position, then I'd throw him back to the wolves and let him get better.
I don't believe there is an injury rating that is visible to the users.
I'm sure someone will correct me though.