I think the 'physical' comment can be taken multiple ways, like he's not strong enough, or he doesn't have the engine to do the running the PL demands, or he can't cope with the physicality of the PL and gets shoved off the ball too easily. It's not as simple as just getting stronger, I know some pretty big guys that you could push over with a nudge because their balance just isn't great.
It's something you can only really learn growing up in a physical league and getting knocked around all the time, he's too far past that now to waste time learning, it's better for him to go and play in another league instead.