This fella is either physically fit or he isn't.
If he isn't then dont have him on the bench. Leave him at home with the physios to work with him and help him get better.
If he is, then he needs matches to get match fit and used to the speed of the Premiiership, and he will only get that by being allowed to set his feet on the pitch. Letting him on for 30secs, or having him run up and down the touchline during a game just wont do it!
For God's sake rafa, do one thing or the other and stop this nonsense.