FG%I key to efficiency

With the end of fantasy football season, people start to pay a little more attention to their fantasy basketball teams. This week starts the stretch of the season that takes us up to the fantasy (and NBA) trade deadlines.

It's a period where owners reconnect with and reassess their squads and begin to ponder major moves.

We've talked a lot this season about the intersection of certain statistics. "1+1+1" players, out-of-position productions, categorical scarcity: These intersections are where we can find unexploited stats that can help us build winning fantasy teams.

Today, I want to get into field goal percentage and percentage-based bias, and use a little homegrown statistic to help overcome that bias.

If points scored is the most overvalued of the major fantasy basketball categories, the percentage categories have to be the most undervalued.

The inherent urge to build a team behind high points-scored totals and other volume-based categories can often be antithetical to building a team that converts a high percentage of its attempts from the field or the line.

What is the most underrated statistical asset a real NBA player can possess? Three-point efficiency. And it's relatively cheap to accrue.

It's a reason why perpetual winners like the San Antonio Spurs compete for a title on a regular basis. If you run a disciplined system, you can find guys who can run to certain spots on the court and hit shots from those spots at a high degree of success for a small amount of money.

Danny Green and Marco Belinelli of the Spurs are prime examples. The Spurs -- as a team -- have hit 40 percent of their 3-point attempts this season.

The Miami Heat employ several NBA senior citizens who still can hit 3-pointers when needed; almost half of Ray Allen's, Rashard Lewis', and Shane Battier's field goal attempts are from downtown. And, of course, they have the most efficient offensive player in the game today in LeBron James (more on him in a bit).

Now, the issue within fantasy is how we apportion field goal percentage, points scored and 3-point production into separate entities.

It's not enough to have a player who hits his shots at a high percentage. It's also important to have sharpshooters who have a high volume of attempts so they can have a beneficial impact on your team's field goal percentage. And you also need players who are efficient from behind the 3-point line.

There needs to be a stat at the center of this diagram.

A little below center, there is a fine metric called Effective Field Goal Percentage that folds 3-point shooting into field goal percentage by accounting for the extra point generated by a successful 3-point shot. That formula looks like this:
Field Goals + 0.5 * 3-pointers / Field Goals Attempted

Kyle Korver currently leads the NBA in eFG% (also known as ADJ FG%) at .667. His eFG% is far higher than his still-solid FG% of .504, because it accounts for his 3-point production. DeAndre Jordan is second in eFG% at .642, which happens to be the same as his league leading FG%, since he has yet to attempt a 3-pointer this season.

We talked about True Shooting Percentage (TS%) earlier this season, a stat that includes free throw production along with 3-point production and 2-point production.

Our own ESPN Player Rater does a fine job at accounting for volume of attempts within field goal percentage. It's all well and good that DeAndre Jordan is shooting 64 percent from the floor, but he only averages 5.7 attempts per game. So he's not going to have as big an impact on your field goal percentages as Andre Drummond, who shoots 61 percent and attempts 9.5 shots per game.

But to give fantasy owners a complete snapshot of the impact an individual player has on his team's field goal percentage, you also have to include 3-point production and efficiency.

Jose Calderon shoots a solid .466 from the floor and averages 9.4 attempts per game. But his secret sauce is the fact that more than half of his attempts are 3-pointers (5.7 per game) and that his 3-point percentage is higher than his overall percentage (.469).

Calderon (when healthy) is perennially underrated in fantasy circles. He's always been below the radar because of his low points per game totals. But when Calderon does shoot, he really, really means it.

Calderon is a big reason why the Mavericks are hanging tough in the Western Conference. Marco Belinelli is a key San Antonio Spur. And just like a real NBA GM uses 3-point efficiency to his advantage, you can use these kinds of players to drive winning fantasy strategies.

Which brings us to the stat I'm going to put at the center of the above diagram.

Last season, I reached out to John Hollinger for some help in compiling a stat that could reflect shot volume, field goal percentage and 3-point production. After some back and forth, we ended up with this:
(eFG%-league average eFG%) * (FGA/gm)/(League average FGA/gm)

Which I call Field Goal Impact, or FG%I for short.

Because I was off last week, I thought it was a good time to put in some extra number crunching and run the top 130 players through the Field Goal Impact formula. (All stats below through Tuesday's games.)

Here is the current top 10 in Field Goal Impact. I've also included their current rank in Field Goal Percentage, so you can see how the addition of volume reshuffles the rankings.

James has actually managed to better his FG%I from around the same time last season (24.31 percent). Last season, LeBron almost doubled his closest competitor (Kevin Durant at 13.72 percent), but some improved eFG%s across the board have raised the bar in 2013-14.

Durant started slow, and his FG%I is now almost back to where it was last season. But now there's a clear FG%I second tier that doesn't include Durant in Korver-Matthews-Calderon-Parsons.

You can really see FG%I's value in how it bumps high-efficiency 3-point shooters like Korver and Matthews from the top 30 in FG% to the top 3. Given their elite 3-point production, and the amount of volume they provide in terms of attempts, it's easy now to see how they benefit fantasy owners in a way that DeAndre Jordan and Andre Drummond are incapable of contributing.

Field Goal Impact also gives proper perspective to players like an Amir Johnson or Marcin Gortat, who both take (and make) a majority of their shots inside the paint.

Here are the biggest risers in terms of their rankings in FG%I versus conventional FG%:

As you can see, the biggest movers are all players who are being rewarded for their 3-point efficiency. It really boosts players like Calderon and Gerald Green who take a majority of their shots from behind the arc.

Conversely, here are the players who took the biggest slide in FG%I rankings versus traditional FG%.

These players tend to be marginal 3-point producers with underwhelming FG% numbers and frontcourt players who should be doing better from the field. FG%I also illustrates how players such as Aldridge and Jefferson, while productive, are suffering in certain statistical areas because they've traded efficiency for volume.

Now let's look at the players who are at the bottom of the league in Field Goal Impact.

Aside from the odd big man having an off year (having Tim Duncan down here is shocking), the dregs of FG%I tend to be players who shouldn't be taking many 3-pointers yet insist on taking as many as the 24-second shot clock will allow.

These are all players who can help fantasy teams, but you have both eyes open when acquiring a Rudy Gay or Josh Smith. They are valuable from a volume-based perspective, but they are doing untold damage to your team's offensive efficiency.

And players can certainly develop while improving their FG%I. John Wall has improved from last season, rising from -13.09% to -7.05%. Monta Ellis was 123rd in FG%I in the NBA; now he's 89th.

Ellis' improved efficiency is another big reason the Mavericks are 19-13 in a tough division. That improvement is generated from what I call The Maverick Effect. Smart teams run systems and find players who might go against the grain who are fits for their systems.

It always pays to run a system, even within the imaginary confines of fantasy.

(And as a special New Year's bonus gift, here's the complete FG%I list)