I was re-watching that great game against the Celtics and was trying to figure out why the Suns had so many turnovers early in the game. Certainly the Celtics caused many (about half) but there were many that were simply "unforced".
I looked close and noticed something quite disturbing. Many of Nash's passes were off.
Instead of hard crisp passes hitting guys in the hands many were lacking zip. Even the ones that connected seemed to arrive around the knees instead of right in the "shooter's pocket" which we are used to. This meant if he drove the lane and kicked to the open shooter and his pass was low it gave the defense time to recover instead of giving our guy an open shot. This would impact assist numbers.
I seemed to recall seeing this recently and so I decided to go all geek up in here and do some quick analysis.
This chart shows that in 10 out of his last 15 perfomances he has been sub-par in assists and/or turnovers. To me, that's a trend.

Data from basketball-reference.com
In this chart which shows 15 games since Jan 20th, we see the main "zero" line which represents the season average and each data point which shows the deviation from that average.
Nash's average APG is 11.5 so a data point of -2 means that he had two fewer assists in that game. For turnovers I inverted the numbers so that if he had fewer turnovers then the average that data point is shown above the line (because fewer turnovers is better).
All this could mean nothing at all but it certainly jives with my sense that he's not been playing as well of late.
Is he hurt? Tired? Resting?
Inquiring minds want to know.