There's been a lot of discussion recently about the increased amount of three pointers taken by the Celtics this preseason. Especially when those shots are being taken by the likes of Jared Sullinger, Jeff Green, and Courtney Lee. Personally I'm a fan of old school basketball, less analytics and numbers, and more hard fouls and driving to the basket. Given this, I'd like to examine why Brad Stevens is encouraging the Celtics to shoot more threes.
Disclaimer: I'm not really a basketball numbers guy so bear with me. I look forward to your insight and critiques.
The basic principal behind focusing the offense on three pointers rotates around shooting percentages. Let's look at an example.
Player A is an average typical player. Player A makes 45% of his field goals and 36% of his three pointers (both league averages for last year.) So Player A takes 10 shots per game, in his first game he shoots only field goals and in the second game he shoots only three pointers. Based on the aforementioned numbers, in the first game Player A scores 9 points. In the second game Player A scores 10.8 points. So to sum all of this up, because Player A shot more threes even at a lower percentage than field goals, he scored 1.8 more points in the second game than the first.
Now, while 1.8 points doesn't sound like a whole lot keep in mind the Celtics have lost three games this season by 2 points or less..... Apparently the Celtics could use those points.
In the above example I used league averages from the past year in order to frame this idea. What I'd like to do now is explore if this offensive concept will work with the Celtics as they are constructed currently. In order to accomplish this, I'm going to suggest we create an idea that I'm calling "the spread."
The spread is essentially the difference between if a player shoots three pointers versus field goals. Allow me to explain with another example.
Player B is a Power Forward in the league. Due to his close proximity to the basket on offense, his FG percentage is 50% (slightly higher than the league average.) However, Player B can't shoot three pointers to save his life, only making 25% of those attempted shots. Now let's run it through again. In game one, Player B takes 10 shots, all field goals, and scores 10 points. In game two, Player B takes 10 shots, all three pointers, and scores 7.5 points. So the spread on for Player B is -2.5 points per game. Player A's spread above would have been +1.8 points per game, so in effect he covered and beat the spread while Player B didn't.
Looking at the Celtics roster, my question is can Celtics players beat the spread so to speak. Let's look at a couple of them and find out.
Sully is apparently being encouraged to shoot more three pointers this season, and I along with some others question this decision. The sample size is small as he only shot 5 three pointers all of last season and only 52 during his time at Ohio State. For the sake of this example, I'll be using Sully's three point percentage from this preseason and his FG% from last season (larger sample size.) Here's how Sully's spread breaks down:
Field Goal percentage: 49% on 111 of 225 shooting 9.8
3 point percentage: 13% on 2 of 15 shooting
So per 10 shots, Sullinger's spread using these numbers is -7.2. So going off of this method Sullinger isn't even close to beating his spread. Granted it's to small a sample size to make a lasting judgement call, but I think it should be concerning to fans that he's being encouraged to take these shots in games. I understand the need for instilling confidence in your players and that they hope to develop Sully in this way, but I'd much rather have him taking shots close to the rim where he's in position for offensive rebounds.
Jeff has shot a ton of threes this preseason. In fact, he's shot roughly 20% of all of the threes the Celtics have shot this preseason. Some people attribute this to Green "coasting" through the preseason, but I wonder if this is the case give some of his recent comments. Given his new found love for three pointers, lets examine Greens' spread, I'll be using Jeff's career numbers for this example.
Field Goal percentage: 45% on 2,025 of 4,513 shooting
3 point percentage: 35% on 355 of 1,028 shooting
So per 10 shots, Greens spread is +1.5. Green in fact beats his spread over his career, but there is one thing I haven't factored into these equations, free throws. Green shot close to 3 free throws per game last season on 80% shooting. You're more likely to get fouled driving to the basket (shooting field goals) versus jacking up three pointers. Obviously, those three free throws could make a big difference when it comes to Green's spread. As one of the few players on the Celtics who is a threat to slash to the rim, I think it's important that Green keeps that two way versatility in his game, but I hope he drives more often than not so he can increase his free throws.
These guys are all really streaky shooters, and I think it depends on what side of a streak they're on if you encourage them to keep shooting the three ball or not. Here again I think free throws come into play. Most of these guys can shoot them at a decent rate, and I'd think we'd want to encourage that perhaps more than three pointers.
Jury's still out on these guys as their NBA careers are just starting. They both show some potential from long range, but it's too early to tell. Kelly seems to have some off the dribble potential so perhaps there's an argument to be had for keeping him out on the three point line. Vitor is a strong rebounder and I'd like to see us mold that, chances are he's no more than a role player, but if he can rebound well he's got a chance at seeing some real minutes.
To wrap this up, I'm not sure that we have a roster catered to what Stevens is attempting to accomplish right now. I mentioned in another thread that I think he's attempting to implement an offensive scheme that we don't have the personnel to be successful with right now. The NBA is different than the NCAA in that you don't get to handpick your players. In college you can recruit the sort of players you want for your offense, whereas in the NBA you're stuck with the players you're contracted to play. I suppose only time will tell, trades may be coming, players may adapt, players may fold, but I'll say this, this new philosophy is concerning to me.