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# Field goal impact

3/12/2013

Winning fantasy basketball strategies lie in the details. And one hazy detail is the true impact a player has on his fantasy team's field goal percentage.

The problem being that field goal percentage doesn't actually paint a full picture in how well a fantasy team shoots from the field.

The gray area exists in the space that lies between shot efficiency and shot volume.

To get the full picture, we need to consider two other factors: a.) the amount of 3-pointers the player converts successfully, and b.) how many shots a player averages per game.

There's already a statistic that depicts factor A. Effective field goal Percentage (or eFG%, or adjusted field goal percentage) accounts for the extra point generated by a converted 3-point shot. If you're into some heavy geekery, here's the formula: Field Goals + 0.5 * 3-pointers / Field Goals Attempted

For instance, Ryan Anderson only shoots 44 percent from the floor (78th in the NBA). But his effective field goal percentage is much a much higher 54 percent (25th) thanks to the large amount of his successfully converted 3-point attempts.

Factor B -- the volume of attempts -- is harder to fold into an existing stat. Tyson Chandler leads the NBA in field goal percentage at 64.7 percent. But Chandler only attempts 6.2 shots from the field per game, barely a third of the 18 attempts Kevin Durant and LeBron James take every night.

Think about it; it takes Chandler almost three complete games to equal the amount of shots attempted by LeBron in a single contest. Chandler shoots 64.7 percent, but LeBron is no slouch at 56.2 percent.

Furthermore, Chandler doesn't bother with 3-pointers, while LeBron averages 1.4 3-pointers per game. That means Chandler's effective field goal percentage remains the same as his raw field goal percentage at 64.7 percent, but LeBron's effective field goal percentage jumps up to 60.0 percent.

Chandler is No. 1 in field goal and effective field goal Percentage. LeBron is No. 9 in field goal percentage and No. 3 in effective field goal percentage.

But Chandler is actually only 4.7 percent better from the floor than LeBron. And LeBron takes almost three times as many shots.

Taking in the full picture, LeBron has a much, much greater impact on a fantasy team's field goal percentage.

No knock against Chandler -- one of the most efficient offensive players in basketball -- but no player comes close to the net positive shooting benefit LeBron provides to his fantasy owners.

The fact that 3-pointers are a fantasy category help include the impact of effective field goal percentage. But I've always thought there should be a statistic that helps delineate the idea of an individual player's field goal impact.

Last season, in trying to reconcile this issue of effective field goal percentage plus shot volume upon a player's true shooting impact, I reached out to John Hollinger, late of ESPN and now with the Memphis Grizzlies.

Hollinger graciously made some suggestions, and I ended up with the following formula: (eFG%-league average eFG%) * (FGA/gm)/(League average FGA/gm)

Which, for simplicity's sake, I'm referring to as field goal impact, or FG%I.

I ran all the players who have logged enough field goal attempts to qualify for the league lead (plus John Wall, because I was curious) through the field goal impact formula. LeBron is No. 1 with a FG%I of 24.3. The player who comes the closest to having no effect (closest to zero)? Mike Conley at -0.14.

Here are 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.

As you can see, field goal impact rewards the players who take and make 3-pointers. The big men who traditionally lead the NBA in field goal percentage are still accounted for (Chandler, Horford, Howard). But the guards and wings who shoot well from behind the 3-point line are also folded in. (Not to mention bigs like Ibaka who make the occasional 3-pointer). And I love how players like Parsons, Green, and Calderon -- quietly, some of the most efficient shooters in the NBA -- get their due.

The one player who throws off the curve? LeBron. The rest of the qualifying NBA players form a nice gradual curve from the bottom & after you get past LeBron, who's 57 percent better than anyone else in the NBA. (I'm not sure LeBron has 57 percent more impact than Durant. As a matter of fact, I'm pretty sure he doesn't. But the rest of the distribution of FG%I holds a remarkable consistency).

Here are the players who received the largest positive boost from the field goal impact formula outside of the top 10. Again, I think this shows how field goal impact can give us a better fantasy perspective.

He's having an off year, but Klay Thompson is not the 102nd-best shooter in fantasy. When you account for volume of shot attempts and 3-pointers, he rightfully climbs into the top 50. Stephen Curry jumps from 76th to 15th thanks to his eye-popping .451 3-point percentage.

Now let's look at some of players who took the biggest slide:

Field goal impact doesn't punish big men for not taking 3-pointers. It just helps gain perspective on the importance of 3-point production in fantasy.

The players Field Goal Impact really punishes are the ineffective 3-point shooters. Josh Smith (a 32.7 percent 3-point shooter), DeMar DeRozan (25.0 percent) and Russell Westbrook (33.9 percent) all took big hits in their rankings because of their relatively low 3-point percentages.

To round things out, here's the entire bottom 10, plus John Wall, who technically doesn't have enough field goal attempts to qualify, but I'm curious to see where he landed.

The interesting fact is how Cousins and Hibbert both sank here despite not being 3-point shooters. The reason they sank is because of their high volume of attempts, coupled with extremely low field goal percentages relative to their position.

I like how field goal impact highlights the flaws in certain players' shooting performances that would otherwise be masked by pedestrian field goal percentages (like Cousins' very average 45.5 percent).

The most frustrating aspect of Rudy Gay's horrific shooting performance this season is that he's actually gotten worse since the trade to Toronto. His field goal impact since becoming a Raptor is a shocking -19.78.

If Toronto continues to slide in efficiency, by the end of the season, NBA teams bound for the playoffs may be able to defend the Raptors with just four players, allowing coaches to rest one player per offensive possession. I actually wouldn't put it past Gregg Popovich.