He's 2x the defender Nash is, I can tell you that much.
While Dirk isn't essentially a top of the line defender, he's also not a defensive liability. He's a body.
Steve Nash is the biggest system player in NBA history. He may be the guy who runs the system, but it's built to perfection as far as complimenting his game. I mean, why wasn't he NEARLY this good in Dallas? I'm still waiting for someone to answer me on that question. And, please don't tell me he developed like some idiot on RealGM said......he left Dallas at age 30.
I can name a ton of PG's who could replace Nash in Phoenix and have similar success.
I'm not a Suns fan or Nash homer but I'll gladly put on my devil's advocate suit just for the sake of the argument.
Regarding his defense, with all due respect, I'll take the opinion of an NBA analyst who sees him every second day over a bunch of knowledgeable Miami and LA fans that see him once every blue moon. More than once, I've heard him called one of the best help defenders in the league, that surely must be worth something coming from Majerle.
Moreover, excluding those comments about him being one of the best help defenders, I have a hard time labeling him a defensive liabillity for the following reason. Nash has one of the best AST/TO ratio in the league. And more often that not as a point guard, by turning the ball over, you create fast break points the other way. In that regard, Speedy Claxton might average 2.23 Steals per game, but that doesn't mean he is as a very good defensive PG considering his 2.23 AST/TO ratio. For example during the Suns recent win streak in a span of 8 games, Nash put up 112 assists to 24 TO's. Ridiculous numbers. On the season, he averages a whopping 16.1 Assists per 48 minutes and 12.1 per game for an AST/TO ratio of 3.23.
Finally, why wasn't he NEARLY this good in Dallas ? I think he was plenty good in Dallas. The main difference is D'Antoni has made him the focus in Phoenix, everything resolves around him, which speaks greatly of him considering their success. In other words, he is the system, has the liberty of calling plays, and running up and down the court. The best reflection of the fact that Steve Nash is not a system player and is a very similar player to what he was in Dallas, only surrounded by better teammates and different coaching, are his stats per 40 minutes. Since joining Phoenix his FG attempts, FG %, 3P % have all gone up which has logically bumped up his PPG's but apart from that his stats per 40 minutes are eerily similar to what they were in Dallas. In other words, Steve Nash in a Mavericks uniform was the same player he is today, only he's been given the keys to the castle in Phoenix and surrounded with athletes that feed off his greatest strenghts which are his vision, creativeness and passing ability.