Expected Zone Shift, 2007-08 to 2010-11

Looking at Zone Starts more and more lately has brought me to the realization that I need something in the back of my mind to remember the expected finishes for players at each level of the spectrum.  To explain, Zone Starts (to horribly butcher and paraphrase these superior descriptions), a concept developed by Vic Ferrari, takes the number of faceoffs that start a player's shift and expresses it as a ratio of offensive zone faceoffs over the total of offensive and defensive zone faceoffs, or O-Zone FO / (O-Zone FO + D-Zone FO).  Pair it with Zone Finish (which does the same equation with faceoffs that end a player's shift) and you have a loose idea of territorial control and coach usage, and the differential (coined "Zone Shift" by Ferrari) gives you a glimpse of whether the player is moving the puck in the right direction.  It's a pretty solid set of metrics, as high Zone Starts have had a positive correlation with Corsi, with the caveat that you need to have a sense of where the league-average Zone Start/Zone Shift is to know a.) players being deployed significantly in their own zone, and b.) whether the Zone Shift is below-average, roughly average, or above-average.  As Gabe's noted in the past, Zone Starts vis-a-vis Finishes pull hard to 50%, so anyone starting at 40% in the O-Zone is far more likely to finish with a positive Zone Shift, and anyone starting at 60% in the O-Zone is far more likely to finish with a negative Zone Shift.

Fun picture time...

I took all the single-season skater performances from 2007-08 to January 31st of the 2010-11 season that had covered at least ~60% of the regular season (50 games in full season; 30 games for this year), put them together, and did Bruce McCurdy's adjustment of moving goals-for from neutral zone finish to O-Zone finish and goals-against to D-Zone finish.  McCurdy expressed Zone Shift by using ranges (in his case, on defencemen in 2009-10), and so I initially wanted to share the data that way as well:

Range -------------- n ---------- Avg. O-Zone Start% ----- Avg. O-Zone Finish% ------ Exp. Zone Shift

<30 ------------------ 7 ---------------- 27.986 ------------------------ 44.619 ----------------------- 16.633

30-34.999 -------- 26 --------------- 32.565 ------------------------ 45.382 ------------------------ 12.817

35-39.999 -------- 91 --------------- 38.195 ------------------------ 46.466 -------------------------- 8.271

40-44.999 ------ 285 --------------- 42.768 ------------------------ 47.838 -------------------------- 5.070

45-49.999 ------ 573 --------------- 47.705 ------------------------ 49.340 -------------------------- 1.635

50-54.999 ------ 670 --------------- 52.240 ------------------------ 51.052 ------------------------- -1.188

55-59.999 ------ 319 --------------- 57.045 ------------------------ 52.263 ------------------------- -4.782

60-64.999 ------- 95 ---------------- 61.943 ------------------------ 52.998 ------------------------- -8.945

>64.999 ---------- 21 ---------------- 68.643 ------------------------ 53.861 ----------------------- -14.782

I wanted to add a bit more complexity to things; as you can see, there are a lot of players bunched in the middle, which takes the average O-Zone start directly into the middle of the 45-49.999 range as well as the 50-54.999.  So instead of sticking with that, I also wanted to express these data by arranging all the Zone Starts from smallest to largest, then breaking them into consecutive buckets of 50 performances (the last bucket ended up being 37).  It resulted in this graph (click to enlarge):

The data:

Bucket (Range) ------------ Avg. O-Zone Start% --------- Avg. O-Zone Finish% ------- Exp. Zone Shift

1st 50 (26.5-36.7) ----------------- 33.046 ---------------------------- 45.513 ----------------------- 12.467

2nd 50 (36.8-39.2) ---------------- 38.294 ---------------------------- 46.599 ------------------------- 8.305

3rd 50 (39.2-40.6) ----------------- 39.956 ---------------------------- 46.948 ------------------------- 6.992

4th 50 (40.6-41.7) ----------------- 41.250 ---------------------------- 47.054 ------------------------- 5.804

5th 50 (41.7-42.7) ----------------- 42.204 ---------------------------- 47.651 ------------------------- 5.447

6th 50 (42.7-43.4) ----------------- 43.048 ---------------------------- 48.114 ------------------------- 5.066

7th 50 (43.4-44.2) ----------------- 43.772 ---------------------------- 48.047 ------------------------- 4.275

8th 50 (44.2-44.8) ----------------- 44.494 ---------------------------- 48.456 ------------------------- 3.962

9th 50 (44.8-45.4) ----------------- 45.126 ---------------------------- 48.337 ------------------------- 3.211

10th 50 (45.5-46.2) --------------- 45.788 ---------------------------- 48.810 ------------------------- 3.022

11th 50 (46.2-46.6) --------------- 46.412 ---------------------------- 49.127 ------------------------- 2.715

12th 50 (46.6-47) ------------------ 46.820 ---------------------------- 48.748 ------------------------- 1.928

13th 50 (47-47.4) ------------------ 47.176 ---------------------------- 49.639 ------------------------- 2.463

14th 50 (47.4-47.8) ---------------- 47.626 ---------------------------- 48.966 ------------------------- 1.340

15th 50 (47.8-48.2) ---------------- 48.048 ---------------------------- 49.518 ------------------------- 1.470

16th 50 (48.2-48.6) ---------------- 48.432 ---------------------------- 49.569 ------------------------- 1.137

17th 50 (48.6-48.9) ---------------- 48.766 ---------------------------- 49.583 ------------------------- 0.817

18th 50 (48.9-49.3) ---------------- 49.138 ---------------------------- 49.890 ------------------------- 0.752

19th 50 (49.3-49.8) ---------------- 49.544 ---------------------------- 50.109 ------------------------- 0.565

20th 50 (49.8-50.1) ---------------- 49.908 ---------------------------- 49.875 ------------------------ -0.033

21st 50 (50.1-50.4) ---------------- 50.256 ---------------------------- 50.221 ------------------------ -0.035

22nd 50 (50.4-50.7) --------------- 50.554 ---------------------------- 50.502 ------------------------ -0.052

23rd 50 (50.7-51) ------------------ 50.882 ---------------------------- 50.714 ------------------------ -0.168

24th 50 (51-51.4) ------------------ 51.228 ---------------------------- 50.996 ------------------------ -0.232

25th 50 (51.4-51.7) ---------------- 51.554 ---------------------------- 50.554 ----------------------- -1.000

26th 50 (51.7-52.1) ---------------- 51.898 ---------------------------- 50.446 ----------------------- -1.452

27th 50 (52.1-52.4) ---------------- 52.236 ---------------------------- 50.951 ------------------------ -1.285

28th 50 (52.4-52.7) ---------------- 52.578 ---------------------------- 51.144 ------------------------ -1.434

29th 50 (52.7-53.1) ---------------- 52.900 ---------------------------- 51.269 ------------------------ -1.631

30th 50 (53.1-53.5) ---------------- 53.302 ---------------------------- 51.694 ------------------------ -1.608

31st 50 (53.5-53.9) ---------------- 53.676 ---------------------------- 51.268 ------------------------ -2.408

32nd 50 (53.9-54.4) --------------- 54.104 ---------------------------- 51.667 ------------------------ -2.437

33rd 50 (54.4-54.9) ---------------- 54.650 ---------------------------- 52.269 ------------------------ -2.381

34th 50 (54.9-55.4) ---------------- 55.150 ---------------------------- 51.639 ------------------------ -3.511

35th 50 (55.4-55.9) ---------------- 55.678 ---------------------------- 51.489 ------------------------ -4.189

36th 50 (55.9-56.7) ---------------- 56.290 ---------------------------- 51.643 ------------------------ -4.647

37th 50 (56.7-57.5) ---------------- 57.050 ---------------------------- 52.220 ------------------------ -4.830

38th 50 (57.5-58.4) ---------------- 57.998 ---------------------------- 53.094 ------------------------ -4.904

39th 50 (58.4-59.5) ---------------- 58.902 ---------------------------- 52.731 ------------------------ -6.171

40th 50 (59.5-60.8) ---------------- 60.086 ---------------------------- 52.876 ------------------------ -7.210

41st 50 (60.8-63.7) ---------------- 62.136 ---------------------------- 53.223 ------------------------ -8.913

42nd 37 (63.7-82.1) --------------- 66.727 ---------------------------- 54.128 ----------------------- -12.599

So there you go.  If I had to say a couple of things about this, for one I would say I was a little apprehensive about the size of groups of 50 at first, but when I saw it play out in the Zone Shift I was put at ease.  The second thing is that if a player is moving from starts at 55% to 52% (as I observed was happening to Alex Ovechkin), that's not a small drop when you look at overall player performances during this period.  It's especially not a small drop if that also puts you in the bottom 3 among forwards on your team when you had previously been in the top 3 for your career.