He will play the best player available at a position regardless of how you set your depth chart(mostly). So he isn't going to do something crazy and play your center at the PG position.
unless his center is better at PG than his PGs are and he already has an other center fielded...
:)
It works like this:
say you have 5 men on the field, and 7 on the bench.
your playing PF needs rest.
What your coach will do is look at the 7 players on the bench and decide which of these 7 would be the best PF and field him.
In most cases nothing odd happens, but if you go to a game with a big variety in players (meaning some very good and some very bad) you could get crazy things.

e.g. say you have 6 very good players, and 6 very bad, and the 5 on the filed are the good, then if he replaces you PF, the 6th good will come in on the Pf, since he's probably the best PF on the bench, but maybe he is actually is a SG. Then 5 minutes later your SG needs to be replaced, and your PF who was benched first is rested now, so he can play SG. You end up with a PF and SG playing opposite positions.
However odd, this COULD happen.
If you know how it works however, you can see such things comming, and according to it can set your tactical decision.
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