One of the toughest things to do when analyzing basketball is to determine how good someone is on defense.
There are a few metrics you can use to attempt to measure their effect on the game, and none of them are true representations of how good an individual's defense might be. You can look at adjusted plus/minus over a large sample size, how they defend certain positions, if they draw charges, or even use counting stats such as steals and blocks.
But ultimately trying to figure out who the best defenders are in some definitive order is a bit of a tall order. In trying to predict who the most effective defenders for this coming season might be, I tried to look at everything that is available at my disposal.
I looked at the on/off reports from NBA.com/stats, the "by position" defensive measurements on 82games.com, the per-possessions defensive numbers of mySynergy Sports, and formulated my own opinion on which players seem to be the best from what I watch on a nightly basis.
This isn't a scientific formula by any means, but merely my best estimation at which players will be the most effective defenders this season, taking into account their individual defensive abilities and how they operate within their own team's system.
I left off young defensive stars like Ricky Rubio, Avery Bradley and Iman Shumpert because we simply don't know their timetable nor their effectiveness from their current injury rehab. Other players like Luol Deng and Josh Smith just missed the cut because their numbers weren't overly impressive.
It's not to say they're bad defenders or not really good; they just didn't make this list of my estimations.