managing defensive replacements

I have Alex Escobar playing RF. I want Alex out of the game when I have a lead, and to replace him appropriately when he gets hurt. I have Matthews in center, and Duffy (a centerfielder only) on the bench. When Alex comes out, I want to send Matthews to RF and Duffy to CF. Do I do this by making Matthews the first defensive replacement and putting him in RF, and then making Duffy the second and putting him in center?
Thanks for any input you have.
Thanks for any input you have.