It's tough to gauge, but as far as on-ice results are concerned, here are the two previous in-season coaching changes:
[TABLE=collapse]
[TR]
[TD]
2018-19
[/TD]
[TD]
GP
[/TD]
[TD]
SF
[/TD]
[TD]
SA
[/TD]
[TD]
SF%
[/TD]
[TD]
GF
[/TD]
[TD]
GA
[/TD]
[TD]
GF%
[/TD]
[TD]
McDavid P/GP
[/TD]
[TD]
McDavid S/GP
[/TD]
[TD]
McDavid +/- per GP
[/TD]
[TD]
Draisaitl P/GP
[/TD]
[TD]
Draisaitl S/GP
[/TD]
[TD]
Draisaitl +/- per GP
[/TD]
[/TR]
[TR]
[TD]
Todd McLellan
[/TD]
[TD]
20
[/TD]
[TD]
630
[/TD]
[TD]
605
[/TD]
[TD]
51.0%
[/TD]
[TD]
57
[/TD]
[TD]
66
[/TD]
[TD]
46.3%
[/TD]
[TD]
1.40
[/TD]
[TD]
3.40
[/TD]
[TD]
0.10
[/TD]
[TD]
1.15
[/TD]
[TD]
2.75
[/TD]
[TD]
0.00
[/TD]
[/TR]
[TR]
[TD]
Ken Hitchcock
[/TD]
[TD]
62
[/TD]
[TD]
1762
[/TD]
[TD]
1994
[/TD]
[TD]
46.9%
[/TD]
[TD]
175
[/TD]
[TD]
208
[/TD]
[TD]
45.7%
[/TD]
[TD]
1.52
[/TD]
[TD]
2.97
[/TD]
[TD]
0.02
[/TD]
[TD]
1.32
[/TD]
[TD]
2.84
[/TD]
[TD]
0.03
[/TD]
[/TR]
[TR]
[TD]
Difference
[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]
-4.1%
[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]
-0.6%
[/TD]
[TD]
+0.12
[/TD]
[TD]
-0.43
[/TD]
[TD]
-0.08
[/TD]
[TD]
+0.17
[/TD]
[TD]
+0.09
[/TD]
[TD]
+0.03
[/TD]
[/TR]
[/TABLE]
[TABLE=collapse]
[TR]
[TD]
2021-22
[/TD]
[TD]
GP
[/TD]
[TD]
SF
[/TD]
[TD]
SA
[/TD]
[TD]
SF%
[/TD]
[TD]
GF
[/TD]
[TD]
GA
[/TD]
[TD]
GF%
[/TD]
[TD]
McDavid P/GP
[/TD]
[TD]
McDavid S/GP
[/TD]
[TD]
McDavid +/- per GP
[/TD]
[TD]
Draisaitl P/GP
[/TD]
[TD]
Draisaitl S/GP
[/TD]
[TD]
Draisaitl +/- per GP
[/TD]
[/TR]
[TR]
[TD]
Dave Tippett
[/TD]
[TD]
44
[/TD]
[TD]
1468
[/TD]
[TD]
1416
[/TD]
[TD]
50.9%
[/TD]
[TD]
143
[/TD]
[TD]
146
[/TD]
[TD]
49.5%
[/TD]
[TD]
1.42
[/TD]
[TD]
3.77
[/TD]
[TD]
0.12
[/TD]
[TD]
1.45
[/TD]
[TD]
3.52
[/TD]
[TD]
0.07
[/TD]
[/TR]
[TR]
[TD]
Jay Woodcroft
[/TD]
[TD]
38
[/TD]
[TD]
1322
[/TD]
[TD]
1231
[/TD]
[TD]
51.8%
[/TD]
[TD]
147
[/TD]
[TD]
106
[/TD]
[TD]
58.1%
[/TD]
[TD]
1.68
[/TD]
[TD]
4.11
[/TD]
[TD]
0.43
[/TD]
[TD]
1.28
[/TD]
[TD]
3.42
[/TD]
[TD]
0.39
[/TD]
[/TR]
[TR]
[TD]
Difference
[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]
+0.9%
[/TD]
[TD]
[/TD]
[TD]
[/TD]
[TD]
+8.6%
[/TD]
[TD]
+0.26
[/TD]
[TD]
+0.34
[/TD]
[TD]
+0.32
[/TD]
[TD]
-0.18
[/TD]
[TD]
-0.11
[/TD]
[TD]
+0.32
[/TD]
[/TR]
[/TABLE]
Both McDavid and Draisaitl have significantly better goal differentials with Woodcroft coming in, but given how much better the goal share is relative to the shots on goal share, it's easy to see that the biggest defensive boost was Smith and Koskinen getting hot after Woodcroft's hiring (0.926 and 0.906 save percentage respectively).
I'm using shots on goal as a proxy for "offensive effort". McDavid "efforts" were worse after the first coaching change (McLellan to Hitchcock). His points per game rose slightly while his goal differential was slightly worse. I'd call that a draw with regards to on-ice results.
For whatever reason, Woodcroft seemed to have resonated with McDavid in particular. Given the descriptions of Knoblauch's coaching style, it seems that there are similarities with Woodcroft. Perhaps that familiarity gave McDavid a big boost in his results (this season's disastrous start notwithstanding).
If we're being fair, McDavid's 2.91 shots on goal per game so far this season would seem to represent the worst "offensive effort" of his career, but using the much-reviled "eye test", it seems that something is ailing him.
Draisaitl did slightly better going from McLellan to Hitchcock. He did slightly worse going from Tippett to Woodcroft, at least in season.
It is worth noting that McDavid (and probably the rest of the team) was going through COVID during the cold stretch in 2021-22, and that Draisaitl likely played through a high-ankle sprain at the tail end of the same season.
------------------------------------------------
One final thing to remember is that McDavid and Draisaitl are entering the "sudden and unexpected" decline ages of many players' careers. The following are the point per game leaders from 2010-11 through 2013-14 (minimum 100 games):
[TABLE=collapse]
[TR]
[TD]
Player
[/TD]
[TD]
S/C
[/TD]
[TD]
Pos
[/TD]
[TD]
GP
[/TD]
[TD]
G
[/TD]
[TD]
A
[/TD]
[TD]
P
[/TD]
[TD]
+/-
[/TD]
[TD]
PIM
[/TD]
[TD]
P/GP
[/TD]
[/TR]
[TR]
[TD]
Sidney Crosby
[/TD]
[TD]
L
[/TD]
[TD]
C
[/TD]
[TD]
179
[/TD]
[TD]
91
[/TD]
[TD]
172
[/TD]
[TD]
263
[/TD]
[TD]
79
[/TD]
[TD]
107
[/TD]
[TD]
1.47
[/TD]
[/TR]
[TR]
[TD]
Evgeni Malkin
[/TD]
[TD]
L
[/TD]
[TD]
C
[/TD]
[TD]
209
[/TD]
[TD]
97
[/TD]
[TD]
154
[/TD]
[TD]
251
[/TD]
[TD]
29
[/TD]
[TD]
186
[/TD]
[TD]
1.20
[/TD]
[/TR]
[TR]
[TD]
Steven Stamkos
[/TD]
[TD]
R
[/TD]
[TD]
C
[/TD]
[TD]
249
[/TD]
[TD]
159
[/TD]
[TD]
126
[/TD]
[TD]
285
[/TD]
[TD]
15
[/TD]
[TD]
190
[/TD]
[TD]
1.14
[/TD]
[/TR]
[TR]
[TD]
Martin St. Louis
[/TD]
[TD]
L
[/TD]
[TD]
R
[/TD]
[TD]
288
[/TD]
[TD]
103
[/TD]
[TD]
199
[/TD]
[TD]
302
[/TD]
[TD]
10
[/TD]
[TD]
52
[/TD]
[TD]
1.05
[/TD]
[/TR]
[TR]
[TD]
Claude Giroux
[/TD]
[TD]
R
[/TD]
[TD]
R
[/TD]
[TD]
289
[/TD]
[TD]
94
[/TD]
[TD]
209
[/TD]
[TD]
303
[/TD]
[TD]
26
[/TD]
[TD]
144
[/TD]
[TD]
1.05
[/TD]
[/TR]
[TR]
[TD]
Alex Ovechkin
[/TD]
[TD]
R
[/TD]
[TD]
L
[/TD]
[TD]
283
[/TD]
[TD]
153
[/TD]
[TD]
132
[/TD]
[TD]
285
[/TD]
[TD]
-17
[/TD]
[TD]
151
[/TD]
[TD]
1.01
[/TD]
[/TR]
[TR]
[TD]
Ryan Getzlaf
[/TD]
[TD]
R
[/TD]
[TD]
C
[/TD]
[TD]
270
[/TD]
[TD]
76
[/TD]
[TD]
193
[/TD]
[TD]
269
[/TD]
[TD]
45
[/TD]
[TD]
182
[/TD]
[TD]
1.00
[/TD]
[/TR]
[TR]
[TD]
John Tavares
[/TD]
[TD]
L
[/TD]
[TD]
C
[/TD]
[TD]
268
[/TD]
[TD]
112
[/TD]
[TD]
149
[/TD]
[TD]
261
[/TD]
[TD]
-30
[/TD]
[TD]
137
[/TD]
[TD]
0.97
[/TD]
[/TR]
[TR]
[TD]
Pavel Datsyuk
[/TD]
[TD]
L
[/TD]
[TD]
C
[/TD]
[TD]
218
[/TD]
[TD]
74
[/TD]
[TD]
138
[/TD]
[TD]
212
[/TD]
[TD]
54
[/TD]
[TD]
49
[/TD]
[TD]
0.97
[/TD]
[/TR]
[TR]
[TD]
Patrick Kane
[/TD]
[TD]
L
[/TD]
[TD]
R
[/TD]
[TD]
271
[/TD]
[TD]
102
[/TD]
[TD]
161
[/TD]
[TD]
263
[/TD]
[TD]
32
[/TD]
[TD]
98
[/TD]
[TD]
0.97
[/TD]
[/TR]
[TR]
[TD]
Henrik Zetterberg
[/TD]
[TD]
L
[/TD]
[TD]
C
[/TD]
[TD]
253
[/TD]
[TD]
73
[/TD]
[TD]
172
[/TD]
[TD]
245
[/TD]
[TD]
34
[/TD]
[TD]
125
[/TD]
[TD]
0.97
[/TD]
[/TR]
[/TABLE]
Crosby, of course, was regularly injured, but it appeared that when healthy, there was no way anyone would ever catch him. He finished a reasonably healthy 2013-14 season with 104 points in 80 games, beating out 2nd-place Getzlaf with 87 points.
Then Crosby turned 27 and scored only 84 points in 77 games, placing 3rd in scoring to Jamie Benn (87 points) and John Tavares (86 points). He would never win another Art Ross, with his closest coming in 2016-17 with 89 points in 75 games, second to McDavid with 100.
This isn't to say that McDavid and/or Draisaitl are definitely in decline or anything like that... but it is something to keep in mind when they appear less effective than they may have been in the past.