If he's not ready because he's hurt, it's a concern.
If he's not ready because he lost months of swings because you can't swing while rehabbing a knee, it's not a concern.
In the 70's, yes. Now, most guys come in ready and in the best shape they'll be in for the entire season. If he doesn't feel the rest of his body is there because he had to rehab is knee, why rush?
You would be the first to complain if he wasn't physically or mentally ready to be on the field. Do you really want a guy that is accustomed to a certain # of swings prior to live pitching or game swings before he's ready? Much ado about nothing.
In order to make the pressure you would feel a little more realistic you should have to make them standing in between "Squirrel Master" and "Nasty Nate".