The 82 games stat line is lineup dependent and considers the offensive efficiency of the players around you as well. Don't particularly care for it and don't believe you get much from it. For example, I can point to the individual lineups (
http://www.82games.com/0708/07BOS8B.HTM) and say that Posey was on the 3 of the top 4 lineups available.
IMO, defensive rating (Opponent's Points Allowed/ Opponent's Possessions) x 100) is a more reflective measure of one's effectiveness on that side of the ball, because it isolates defensive measurements as opposed to throwing out offensive effectiveness in a total rating. You can look at an individual's TS% and turnover statistics as a measure offensive efficiency. It doesn't punish a player for playing with Glen Davis or Tony Allen like the 82 games stat.
On a side note ... suggesting Matt Barnes is a good defender is
laughable. The guy rates closer to the bottom quarter in almost every defensive statistic that normalizes individual play. How exactly is he a good defender? Defensively, he's been well below average on every team he's been on ... so you can stop blaming Don Nelson for Matt Barnes poor defensive stats.
I have no qualms saying he had a good series against Dallas. Good for him. Doesn't change his play on the defensive side of the ball. The guy is a similar defender from an effectiveness standpoint to Ricky Davis, who is a sieve. Even with the Dallas series in his wallet, he also struggled down the stretch this year when Golden State needed him.
There are better options than Matt Barnes. I'd rather have Maurice Evans than Barnes. He doesn't struggle defensively and provides the same type of outside shooting. I'd rather have Ricky Davis. He offers more offensively than Barnes for the poor defensive play you are likely to see for both AND he probably takes a 1 year contract.
On a positive note, atleast Barnes has made his turnover ratio just mediocre as opposed to awful.
Barnes is better than Tony Allen, but a poor replacement to Posey. He offers an outside shot, but is a downgrade in almost every other attribute.