I have been saying this for 5 years since Manu was moved to the bench in favor of the psychologically fragile Hedo. For the same amount of minutes played, it takes a much bigger toll on Manu's body to play off the bench.
I'll use a very simple example (this is just a simple example to show the point, I am not arguing for any specific pattern). For the first half of a basketball game (24 minutes), let's use the following two rotation patterns (showing just playing time) that use the same number of minutes total (16 minutes in this example).
Starter:
1st Q: 12:00 - 04:00
2nd Q: 08:00 - 00:00
This gives you a pattern of 8 minutes playing time, 8 minutes of rest, 8 minutes of playing time for a total of 16 minutes playing time.
Bench:
1st Q: 06:00 - 00:00
2nd Q: 12:00 - 10:00
2nd Q: 08:00 - 00:00
This gives you a pattern of 8 minutes playing time (6 in the 1st Q + 2 at the beginning of the 2nd Q), 2 minutes of rest (2nd Q 10:00 to 08:00), 8 minutes of playing time for a total of 16 minutes playing time.
Note that I have ignored the break between quarters and teams' timeouts for the sake of simplicity in the explanation.
Given the two usage patterns above, which of the two you believe is better to maximize rest?
If you are not convinced, let me give you a specific situation to further clarify the point. If you are asked to run the longest distance you can, and you have to following two options:
a) 8 minutes running, 8 minutes resting, 8 minutes running
b) 8 minutes running, 2 minutes resting, 8 minutes running
For a total of 16 minutes running time. Do you think you can run a longer distance using (a) or (b) pattern? Which one you would pick?
From the pure physical/endurance point of view, the critical point here is that by coming off the bench you lose the initial minutes of the 1st Q that you are not playing, BUT you are not resting either. Players have at least 24 hrs of resting before the game (at least in a back-to-back, they usually have 48, 72 or 96 hours), so resting 24 hrs or 24 hrs + 6 minutes makes no difference for them. However, the resting time in between playing periods during the game is critical.
One could also argue that having to lead the offense with the 2nd group and being the primary focus of the defense during that time (which it is important but a bit more difficult to measure quan atively), it also takes a larger toll on the body, since you have to constantly create for others and you have less quality players to play with you. This may be somehow compensated by the less quality of opposing players, but the rotation patterns of different teams usually do not align perfectly except under very specific cir stances for certain players (like a defensive specialist just to guard a specific player). This is usually clearly seen when you calculate adjusted +/- stats, but this is not the point.
If the ultimate goal is to maximize rest, then it is absolutely clear that for the same amount of minutes played, it takes a much bigger toll on Manu's body to play off the bench.