Murphy is spot-on with Yelich's back and you can tell which posters just don't have any experience with that sort of thing. I had the exact procedure that Yelich had. "Rest" doesn't help you, it doesn't have anything to do with it.
Once you've had that injury, your spine will never be what it was. You can have surgery and do yoga and strengthen all those core muscles, which he has clearly done to be as effective as he is, but all it takes is one slip, one goofy step off a staircase, sitting in a stool just precisely the wrong way, and you're flared up and have to start over. The worst part is that "rest" as people know it just makes everything worse. Once you're hurt, you have to strike a perfect balance between activity and rest.
You need to be active enough to keep things loose there, but not so much you make the strain worse. And you have to keep that game going until things feel good again, which can be days or weeks. Back stuff is completely unpredictable. But giving him a random day off when he feels healthy isn't going to help him and mixing in a random day off isn't anywhere close to the time it takes for a nerve to reheal or for a partial reherniation to subside.