First real thread here, and I hope to get some feedback.
I've been pondering how to capture defensive impact (and team offense impact) better through stats, and stumbled on a neat stat used in NHL circles called With Or Without You's (WOWYs). It is fairly simple - it just separates a player's stats into how the team and individual performs when he is playing with a particular teammate (or lineup) versus not with that teammate (or lineup).
Now, as far as I can find, there's no readily available version online for basketball, but I figure I can cobble something together from basketball-reference's On/Off splits and lineup finder. So I thought I'd try to take a look at the Raps and see what impact our players have on their teammates. I won't be able to see individual stats based on lineups (which is what WOWY really is, and I hope to find a way to look at that too), but the way the team performs when the players are on the court together is really what matters, so I'll look at that. This will be similar to the approach taken with adjusted plus-minus and RAPM, except I'll be targeting the impact on lineups with specific players.
What I'm interested in is how our pieces fit together - not so much the Gray's and Acy's of the world, but how our primary and secondary pieces either help or hinder the performance of our core pieces.
First, a list of the players and their impact on and off the court last year in general. I've also included the most used guys who are off the team now, as well as the new guys.
Player - ORTG On - DRTG On - ORTG Off - DRTG Off - Net Impact
DD: 105.3 / 107.3 / 109.4 / 109.5 / -1.9
Amir: 109.7 / 104.9 / 101.5 / 111.9 / +15.2
Lowry: 107.9 / 107.3 / 104.5 / 108.4 / +4.5
JV: 104.0 / 107.7 / 107.6 / 107.9 / -3.4
Ross: 106.4 / 109.2 / 106.2 / 107.2 / -1.9
Gay: 106.7 / 104.0 / 106.1 / 109.1 / +6.0
Fields: 108.4 / 108.4 / 105.5 / 107.6 / +2.1
Gray: 98.8 / 107.3 / 107.4 / 107.9 / -7.9
Acy: 113.8 / 99.8 / 105.6 / 108.6 / +16.9
Hansbrough: 100.6 / 100.4 / 107.0 / 99.6 / -7.1
Augustin: 100.3 / 102.0 / 106.8 / 99.0 / -9.6
Daye (DET/MEM): 107.4 / 105.5 / 104.4 / 104.5 / +1.9
Novak: 112.2 / 106.5 / 110.6 / 107.0 / +2.1
AA: 106.7 / 110.3 / 106.0 / 106.4 / -3.1
ED: 104.5 / 109.2 / 106.9 / 107.4 / -4.2
Bargs: 104.6 / 110.8 / 106.8 / 106.8 / -6.2
JL3: 105.4 / 111.5 / 106.5 / 106.9 / -5.7
So, yeah. I'm pretty glad we got rid of AA, Bargs and JL3. And as much as Eddy was a nice young piece to have, he wasn't exactly setting the world on fire in terms of impact. And those new additions don't exactly inspire confidence (Daye was awesome in DET and terrible in MEM, balancing out to that fairly even score you see above). Now, these are simple plus-minus stats, so mean little by themselves and are prone to problematic conclusions, but that's why I'm going to look at some lineup data next.
So, what impact does each of these players have on their teammates? Let's use an example to go through in detail. I'm going to use Fields as an example, as he is touted by many (myself included) as an impact guy in spite of his individual numbers.
Player - ORTG with Fields - DRTG with Fields - Net RTG with Fields - MP with Fields
DD: 105.3 / 107.3 / -3.9 / 702
Amir: 109.7 / 104.9 / +4.9 / 516
Lowry: 107.9 / 107.3 / +4.1 / 475
JV: 104.0 / 107.7 / -3.3 / 308
Gay: 106.7 / 104.0 / +3.8 / 162
From here, we can extrapolate back from their season total numbers to get a "Without Fields" number, and find the difference between playing with Fields and without him. Keep in mind that a positive value in DRTG change is a bad thing.
Player - ORTG impact from Fields - DRTG impact from Fields - Net RTG impact from Fields
DD: +0.5 / +3.0 / -2.5
Amir: +1.3 / +1.2 / +0.1
Lowry: +5.1 / +0.5 / +4.6
JV: +3.0 / +2.5 / +0.5
Gay: +0.8 / -0.5 / +1.3
So you can see that generally speaking, Fields playing in the same lineup as DD is a bad idea - which supports the backup SG role for Fields, letting him play some with Gay while DD sits, or play SF with Ross at SG (as a note, Ross had a +9.7 WOWY with Fields). In fact, of all the players from last year that were retained, only DD had a negative Fields WOWY. The interesting thing of note here is that I expected Fields to hurt the team offensively, and help enough defensively to make up for it. However, the opposite seems to be true in most cases. He's a small negative defensively, and a more significant positive offensively. Note that he has good impacts particularly on Gay and Lowry - two aggressive scorers that draw a lot of attention, and can find a guy on a back door cut. Also note that Gay improves offensively and defensively when playing with Fields.
So, here's how the rest shape up. I'm looking at how our core fits together, plus how some "core hopefuls" such as Fields complement them. So I'll be doing DD, Gay, Lowry, JV, Amir, Fields and Ross (not Acy or Gray due to small sample size and I don't care, respectively). Plus I'll throw Bargnani on there just to show how much of a detriment he was while he was on the floor (if the first set of stats above wasn't clear enough).
Player - ORTG impact from DD - DRTG impact from DD - Net RTG impact from DD
Amir: -2.9 / -6.6 / +3.7
Lowry: -11.0 / -6.5 / -4.5
JV: -3.3 / -4.0 / +0.7
Gay: +0.5 / -1.5 / +2.1
Does not do well with Lowry. Otherwise is at least passable. Nothing big in either direction here.
Player - ORTG impact from Gay - DRTG impact from Gay - Net RTG impact from Gay
DD: +2.2 / -5.2 / +7.4
Amir: -1.2 / -5.6 / +4.3
Lowry: -2.3 / -8.3 / +6.0
JV: +8.7 / -9.4 / +18.0
Gay definitely had a big positive impact here.
Player - ORTG impact from Lowry - DRTG impact from Lowry - Net RTG impact from Lowry
DD: +2.1 / -2.3 / +4.4
Amir: +5.8 / -1.9 / +7.7
JV: +0.3 / -5.0 / +5.3
Gay: -0.4 / -5.9 / +5.5
Yep, Lowry fits well with this core. Solid PG.
Player - ORTG impact from JV - DRTG impact from JV - Net RTG impact from JV
DD: -3.1 / -0.3 / -2.7
Amir: -1.1 / -6.4 / +5.3
Lowry: -7.4 / -2.5 / -4.8
Gay: +5.2 / -4.0 / +9.2
Big swings here, and I expect a lot has to do with his progress from the first half of the season to the second. I think I'll filter by half season.
Player - ORTG impact from JV 1st Half - DRTG impact from JV 1st Half - Net RTG impact from JV 1st Half
DD: -6.5 / +5.4 / -12.0
Amir: -17.2 / -7.3 / -9.9
Lowry: -12.6 / +6.8 / -19.4
Player - ORTG impact from JV 2nd Half - DRTG impact from JV 2nd Half - Net RTG impact from JV 2nd Half
DD: 0.0 / -5.8 / +5.8
Amir: -0.2 / -8.1 / +7.9
Lowry: -4.2 / -12.3 / +8.1
Yep. What a difference. It helped that he played a lot more with Amir in the 2nd half, though that would definitely not account for these big WOWY changes. Why would Casey only play JV and Amir together a total of 24 minutes in the entire first half of the season? Insane. But still, who sees improvement like that mid season? Crazy pants. If he makes half the same progress in his game between the end of last season and the end of this coming one, we've got ourselves a player, guys.
Player - ORTG impact from Amir - DRTG impact from Amir - Net RTG impact from Amir
DD: +8.9 / -9.7 / +18.6
Lowry: +11.6 / -8.5 / +20.1
JV: +7.0 / -11.5 / +18.5
Gay: +7.9 / -9.6 / +17.5
Amir is hilariously awesome. He makes everyone around him SO MUCH BETTER. I might have to revisit my stance that we don't need to move Amir to tank - if we want those losses to pile up, he has to be the first to go. And if we want to be good, we've got to have him on the court as much as possible. Just because Amir is so awesome, I'll list his impact on everyone else as well.
Seriously. The only player on the roster that had a negative plus-minus while on the court with Amir was Gray (I include all the scraps and garbage like Pietrus I've left out above), and he's just a lost cause.
Player - ORTG impact from Ross - DRTG impact from Ross - Net RTG impact from Ross
DD: -5.2 / +2.4 / -7.6
Amir: +1.3 / +2.4 / -1.1
Lowry: +3.9 / +3.9 / 0.0
JV: -11.6 / +5.5 / -17.1
Gay: -1.5 / -3.0 / +1.4
Ross and Valanciunas, as you'd expect from two rooks, just proved too raw to be on the court together. Ross does not match up well with DD either. His slight positive impact on Gay suggests either a good fit or improvement towards the end of the year.
And the piece de resistance... And the single biggest reason to think the team improves this year over last (maybe besides Jonas' insane improvement).
Player - ORTG impact from Bargs - DRTG impact from Bargs - Net RTG impact from Bargs
DD: -0.7 / +3.5 / -4.2
Amir: +0.8 / +4.6 / -3.8
Lowry: -5.5 / +4.1 / -9.5
JV: -1.5 / +5.0 / -6.5
Gay: +0.4 / +7.8 / -7.4
Anyway, I hope you guys get something from this. Feel free to critique and question - I've got a whole spreadsheet set up and can make changes where you think it necessary or informative.