“Get good looks” is a common phrase in basketball Coach Speak. It means: try and break down the defense to create good, open shots. Generally speaking, open shots are higher percentage. Covered shots are lower percentage. But can we measure what “higher percentage” actually means? Let’s try.
As long as zones aren’t involved, a typical defensive set begins with picking up an offensive player. That player is now being “guarded.” As long as his defender follows him within reasonable distance for the rest of the possession, he will still be guarding him. Occasionally, “reasonable distance” creates some ambiguity, but the majority of the time a defensive assignment is quite clear.
When a player takes a shot while still being guarded, whether it’s in the post or off the dribble, it’s a “guarded” attempt. So, how do players lose their defender and become “unguarded?” Typically this occurs in one of the following ways:
- Due to defensive errors
- In transition
- From screens
- Off of double teams
Rotations and help defense allow a defensive player to switch onto someone else during a possession. This happens a lot on penetration or double teams. Using this methodology, closeouts on open shots are not guarding situations (unless the defender literally blocks the shot). Which means screens, double teams and transition opportunities provide the majority of “unguarded” shots in a game.
Some examples of “guarded” attempts:
- Michael Jordan’s Game 1 shot over Bryon Russell in the 1997 NBA Finals
- Hakeem Olajuwon’s ultimate Dream Shake on David Robinson
- Magic Johnson’s 1992 All-Star game 3-point finale
- Getting. Dunked. On.
Some examples of “unguarded” attempts:
- John Paxson’s game-winner in the 1993 NBA Finals
- John Stockton’s shot to send Utah to the 1997 NBA Finals
- Michael Jordan’s “flu” game-winner in the 1997 NBA Finals
- Robert Horry’s game-winner in the 2005 NBA Finals
I tracked all 164 playoff games from 2010 and 28 games from 2011 thus far. I get the following results:
1. Human error does exist. There are ambiguous possessions with pseudo-screens or quick-hitting action that create the potential for mistakes. Heck, despite best efforts, notational mistakes occasionally occur as well. Although that’s not necessarily too different from a standard box score, since I’ve seen FGA’s not counted, phantom assists and fouls called on bench players. Still, the data are not perfect.
2. The varying difficulty of 2-point shots. 2-point shots include wide open layups and 23-foot jumpers with Dwight Howard running at a shooter. These numbers are a starting point, not a definitive conclusion, so for the sake of simplicity these events are both “unguarded” shots. However, the 23-foot shot is clearly harder than a layup when a player is wide open. It’s becomes an even lower percentage attempt with a giant leaper running out at the shooter.
3. Perhaps because of point No. 2, 2-point% has a much higher variance than 3-point%. The difference in 3-point% and the accuracy of “unguarded” 3-point shots has been fairly consistent since I began tracking this stuff, right around an 11-13% difference. However in smaller samples, 2-point% has varied from a 10-20% difference, depending on environments, teams, and offensive players involved.
4. Dividing two-point shots by location would obviously provide a better idea of percentage difference going forward. Layups, we can safely assume, are converted at an incredibly high rate when they are open. But after that, it’s likely that there is a dropoff in percentage the farther away from the hoop we go, whether a player is guarded or not. It might be interesting to note these differences by floor location.
Nonetheless, these results at least give us a good ballpark as to what happens when players are able to lose a defender, for a myriad of reasons, and take higher percentage shots.