Introducing Field Goal Impact
During last week's discussion of categorical scarcity, I mentioned that in a later column, we'd be looking a little more deeply at the true impact of a player's cumulative effect on a fantasy team's performance from the field. That is, how much a player is really impacting your team's field goal percentage.
Well, I knew I couldn't just throw out a proposition as tantalizing as that and not follow through. Unlike Paul George, I am not a roto tease.
Specifically, I want to approach it from the perspective that it isn't merely enough just to look at who has the best and worst field goal percentages (FG%) when gauging which players are helping and hurting you the most, because two other factors are at play: 3-pointers converted and field goal attempts (FGA).
Adding 3-pointers and FGA to the conversation helps factor in two key components: efficiency and volume. It's not enough just to list who has the highest and lowest FG% and leave it at that, because it penalizes players that give you 3s and distorts the conception of which players are actually making the largest impact on your team's field goal percentage.
I figured there was some next-level stat I hadn't heard of that guys like Daryl Morey carry an app for on their iPad (and I don't even have an iPad). There are stats I use all the time that can point us in the right direction, but nothing I'd ever heard of to specifically balance a player's shooting efficiency with volume of shot attempts.
One stat I love in this general area is true shooting percentage (TS%), which delineates how often a player generates points per attempt, be it from the field or the free throw line. (It's the reason why I've always been such an admirer of Chauncey Billups, the TS% king).
But I was searching for a stat that first of all removed the free throws from the TS% equation, leaving us with just 2-point and 3-point field goal attempts, then factoring in that with a player's comparative shot volume.
There's a stat called points per shot (PPS) that measures how many points a player generates per field goal attempt (Dwight Howard leads the NBA at 1.53 PPS, with LeBron right behind at 1.52). But that wasn't quite it, since it leaves out volume.
So I asked the marvelous ESPN Stats & Info department, who have been invaluable this season in helping me figure things out that normally would have required me to quit my day job(s) to grasp. And they, very correctly, pointed me towards effective field goal percentage -- also known as adjusted field goal percentage -- or eFG% if you're nasty.
Effective field goal percentage takes points per attempt, and turns it into a percentage, adding 3s into the equation. The formula looks like this:
(FG + 0.5 * 3P) / FGA
Stats & Info was kind enough to give me a list of the current NBA leaders in eFG% that are also averaging more than 10 field goal attempts per game. So this list, by removing the low-volume shooters, gives us a rough idea of what I'm talking about (hint: the league average eFG% is 48.1 percent, and anything above 52.0 percent is pretty darn good).
This list is a great CliffsNotes version of players to target when looking to boost your team's field goal percentage. It's useful because it shows a true representation of which players are giving you an extra, hidden boost due to their 3-point prowess. Which, by the way, makes Kyrie Irving our front-runner for eFG% Rookie of the Year.
Now, I'll add on to that myself by giving you some of the NBA's worst eFG% offenders that average more than 10 FGA per game (hint: anything below 45.0% is pretty darn bad).
Conversely, the most damning names on this list are the players not known for 3-point attempts, which basically makes it a one-name list. Congrats, Amare.
But I was going for exactitude. If this elusive stat wasn't available readily on ESPN.com, or Basketball-Reference.com, I was going to have to go right to The Source.
Now, I've never approached John Hollinger about anything in my life, because my fear of people I admire is legendary. (This is due to a brief encounter I had with Lou Reed when I was an intern at Late Show with David Letterman that still supplies me with 2-3 nightmares per year.)
Anyway, this seemed pretty important -- I never want to let any of you down -- so I went right up the ESPN food chain, marshaled my courage, and e-mailed The Source. Lo and behold, I found out two things: 1. John Hollinger is a perfectly nice and approachable person; and 2. The stat I was looking for did not exist.
This was exciting to me; a stat so obscure that only I was apparently interested in it? I threw out a few examples of stats I thought could be applicable to this nonexistent stat (usage rate, eFG%, FGA per game), and Hollinger, just as I hoped he would, whipped out this formula:
(FG%-league average) * (FGA/gm)/(League average FGA/gm)
This was wonderful, but I added one small touch, including the 3-point factor by changing the FG% part to eFG%, thereby colliding Stats & Info's chocolate with Hollinger's peanut butter. The resulting formula:
(eFG%-league average) * (FGA/gm)/(League average FGA/gm)
For right now, we'll call it field goal impact (FG%i). I ran all the top effective field goal players through the formula, and came up with this ranking:
Top 20 in field goal impact, 2011-12 season
To me, this feels about right, because it slightly reshuffles the eFG% rankings in favor of the players with the highest volume of field goal attempts. It puts LeBron ahead of Ray Allen, which is fair, since he attempts twice as many shots (20.5 FGA versus 10.0 FGA). It also shoves Marcin Gortat down a few pegs, since Gortat stays within 12 feet of the basket (and we love him for it).
Just remember that this stat isn't a percentage, it's a score. The average NBA player should have a FG%i of zero. If zero is the mean, it dictates that the players who are harming your field goal percentage will have a negative score.
Lowest field goal impact, 2011-12 season
As someone who manages to masochistically watch every Wizards game, it wasn't a shocker to see Wall is No. 1 with a bullet. What FG%i did was bump up high-volume shooters like Amare and Granger ahead of players like Kemba Walker and Monta Ellis. See how Amare surges ahead of Carmelo due to his attempting five extra shots per night? The stat, in an unrefined way, appears to work.
Here's the FG%i for five other high-volume shooters with more middle-of-the-road eFG%:
Personally, I'm digging this because it's showing Bargnani's hidden value (something I've been pushing for a long time). It would put Bargnani right below David Lee in the NBA hierarchy, which again feels about right. It shows that Kobe will have only a small effect on your team's field goal percentage (unless the rest of your team has a particularly high or low FG%), and you can enjoy his high-volume stats with a guilt-free conscience.
Again, this is a very unrefined stat. There are people smarter than I who could really hone this down. But at the least, this would have made for a fine ninth-grade science project. I do think it points to a small hole in our statistical galaxy, one that's especially important when examining stats from a fantasy perspective.
John Cregan is a fantasy basketball analyst for ESPN.com. Follow him on Twitter @JPCregan.
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