Normally, I’d wait for the playoffs to conclude before really digging into this summer’s free agency. But the free agent class of 2010 is so good, and the face of the league could change so much, I think an early look is warranted.

A few months ago, I updated my list of the Top 10 NBA Free Agents of 2010, and not a whole lot has changed in terms of the overall rankings of these players.

I thought it would be interesting to look at the five best free agent big men — Chris Bosh, Amare Stoudemire, Dirk Nowitzki, Carlos Boozer and David Lee — and compare them using a variety of statistics. Here is what I found:

(As always, click on the table to see a bigger version.)

All of the stats in Table 1 should be familiar to most NBA fans. % GP represents the number of games in which a particular player has appeared, so the lower the number, the more games the player has missed due to injury or other reasons. I’m not 100% clear on Lee’s rookie year — I don’t know if he missed time with injury or just did not play because the coach didn’t put him in. He has been very durable the last three years, appearing in 81 games each season. Stoudemire and Boozer are clearly the biggest injury concerns of the bunch, but both players have stayed healthy this season. Stoudemire’s FG% (55.7%) is very impressive, while Bosh brings a bit of three-point shooting to the table.

All of the stats in Table 2 are adjusted for team pace (i.e. possessions per game). So if a player plays on a team that really pushes the ball (like the Suns or the Knicks), they will get more possessions on average to score, rebound, assist, etc. These stats are adjusted so that pace is eliminated.

They are also “per 40” stats to account for the difference in minutes played. This levels the playing field so we can look at all of these stats without pace or minutes played bias.

To me, Nowitzki is the best scorer of the bunch. Bosh’s numbers are also very impressive considering that he doesn’t play with a great setup guy like Stoudemire (Steve Nash) and Boozer (Deron Williams) do. Boozer and Lee are clearly the best passers of the bunch, though defensively they get more steals than blocks. It’s the other way around for Bosh, Stoudemire and Nowitzki.

Here is where the stats can get a little sticky. Adj PER is from Hoopdata and is an adjustment of John Hollinger’s Player Efficiency Rating that uses actual assisted and unassisted field goals, as well as charges. (Hollinger’s version does not.) PER Diff is from 82games and refers to the difference in PER between the player in question and his counterpart on the opposing team. For example, Bosh (+12.5) vastly outplayed his opponent, while Lee (+2.9) did not. (Of course, this might have something to do with Lee playing out of position the entire season. It’s tough to cover centers when you’re 6-9.)

PPS (Points Per Shot) is simply the total number of points scored by the total field goal attempts, so players that get to the line and those that can shoot the three will have an advantage here. TS% is a weighted efficiency, adjusting for three pointers and free throws. (By the way, I prefer PPS since the equation doesn’t have any arbitrary constants.) Adj EPM takes my Efficiency Per Minute statistic and adjusts it for team pace. Net Prod. comes from 82games and refers to the difference in production between the player and the opponent when the player is on the court. On/Off (also from 82games) refers to the difference between the on/off scoring for a particular player. For example, Boozer has a -2.2 On/Off number, but that may have to do with the fact that he has a very good backup in Paul Millsap. There is no one of that caliber playing behind Bosh or Nowitzki.

Moving left to right, I’ve already mentioned how Lee had to play out of position, and how that might have impacted his PER Diff. Boozer also played a lot of minutes at center, but his Per Diff was the same for both positions. Stoudemire is the most efficient scorer in terms of PPS, but Bosh finished a surprising second in this category. Stoudemire isn’t the greatest rebounder, however, and that hurts him in Adj EPM. Boozer’s aforementioned -2.2 in On/Off can be at least partially explained by the quality of his backup (Millsap). Lee’s -1.3 in this category is a little worrisome.

DEF (from HoopData) is the average sum of blocks, steals and charges per 40 minutes. (As a reference, Andrew Bogut led in this category with 4.73, while Dwight Howard posted a 4.29.) ORR (Offensive Rebound Rate), DRR (Defensive Rebound Rate) and TRR (Total Rebound Rate) refer to the percentage of rebounds that each player gets during his time on the court.

eFG% Allow Diff is an 82games stat that provides the difference in effective FG% when the player is on and off the court. The more negative the number, the better. eFG% Pos Allow refers to the effective FG% that the player’s positional counterpart produced while the player was on the court. Again, the lower the number, the better.

Moving left to right, it’s interesting to see that Nowitzki and Stoudemire are the top two players in DEF, as they both have reputations for being lackluster on the defensive end. Stoudemire is about as good on the offensive glass as Bosh (and better than both Boozer and Lee), but he is the worst of the bunch on the defensive glass. It would make sense for a team to pair him with a power forward or center that relishes cleaning up the defensive glass (like Boozer, for example). Boozer is the best overall rebounder of the bunch, and that’s especially impressive considering he plays a lot of minutes with another stellar rebounder (Millsap).

In terms of eFG%, Boozer’s numbers could be impacted by the quality of Millsap. In terms of positional eFG%, Boozer (51.8) is better than Lee and pretty close to Bosh. Stoudemire’s positional eFG% (47.4) is surprisingly good. Maybe he’s not as bad of a defender as he’s made out to be.

So what does all of this mean? To me, aside from the injury concern, maybe Bosh and Stoudemire are closer in value than currently perceived. Bosh is a year-and-a-half younger, so his prime should last longer than Stoudemire’s. Still, if a team can’t land Bosh, Amare is a nice Plan B.

Boozer and Lee are an interesting comparison. Lee is more durable, but Boozer’s offensive and rebounding numbers are slightly better across the board. Defensively, neither player is worth writing home about.

One thing that occurred to me, if I were running the Heat or Knicks (two teams that can add two big-name free agents), it may not be a bad idea to pair Stoudemire with a power forward like Boozer or Lee, who can offset Amare’s mediocrity on the defensive glass. This is especially true for the Knicks, who could actually play Stoudemire at center much of the time.

Value-wise, I think Bosh and Stoudemire will both end up with “max” contracts, while Boozer and Lee will have to settle for less. Boozer will probably command a higher annual salary, and that should make the more durable (and almost as productive) Lee the better value.