It's at least nice to know (or think) that there is a reason for his poor performance. It does beg the 'injury prone' question which could hurt his trade value if he is discussed this off-season.
I think anyone who is as aggressive as he is on defense is injury prone. Guys like Delonte and Gerald Wallace put their body on the line.
We shouldn't think that 'injury prone' is some intrinsic quality (though it is for some who have physical defects). It is more commonly a random illusion, the result of an injury not healing properly, or a result of style of play. D Rose might be in the last category due to the stress he places on his joints changing direction on the hop.
There is a good reason to hold back a little. This reminds me of Kobe saying how he doesn't draw charges. There are things you can do to keep yourself on the floor. Bradley does not have the option to hold back at the moment because his defense is what gets him minutes.