Can someone explain how a defensive replacement is determined?

Specifically if I have....

Who on first and expect him to be subbed out and Who's first replacement on the list is What. BUT What is already in the game playing second base. What happens?

Scenario #1...Does What move to first base replacing Who and someone else comes into the game at second base?

or

Scenario #2...Does Who's #2 replacement come into the game and What stays at second?

If Scenario #1 takes place does Simmy take into account any defensive ratings if any of the switching does happen? In Scenario #1 happens and What moves to first base will What not be shifted over if his replacement at second base does not have as good of defensive ratings?

Was a serious question

I believe simmy would go with scenario #2. They typically don't move players around when bringing in defensive replacements (though I've had situations in the past where I wished simmy would do that).

The question was confusing so that's probably why you didn't get answers.

As a general rule, Simmy will using your D-R and move 1 player.    For instance, DR SS takes SS, my SS is #1 on 2B DR list.  He moves to 2B and 2B finds the pine.  He doesn't move to 3B or LF even if he's #1 on those lists after coming out of game.

Ok 1 level movement not multiple levels. Thanks Mike

my question about defensive replacements is this. If player A is your starting 2B and player B is the first defensive replacement will the sim put player B in even if player A is better defensively?

Yep.  Make the change. 

that's what I thought. makes no sense though. why make a defensive replacement with a guy who plays worse defense?

The SIMMY does what you ask it to do.   Mostly.