I will say Nash looks a LOT leaner. That looks like 2003-2004 Nash, body-wise.
To me the biggest issue that will affect his production will be a willingness to go into high traffic areas. That was obviously lacking last year and really affected his production. As I and many speculated it WAS due to the concussions, he admitted as such in the Post article he was "uncomfortable" in physical situations.
Going to the net has been a huge part of Nash's past production. It was clear as day last year that he was ripping lots of crappy perimeter shots yet many were reprimanded for calling this out. "His avg shot distance hasn't changed much", "his Corsi was fine" - yet here we have Nash admitting he didn't get to the inside enough last year. I honestly like Corsi but I don't understand the dogmatic approach to all shots being created equal. Quality matters a significant amount.
Hopefully Nash is willing to drive the net and being leaner helps his endurance later in games and in the season.