The issue of replacing a promoted minor leaguer has come up twice lately. This post was also added to the Week 12 thread and links to the ruling regarding this that was posted pre-season.
Here is a link to a post from this spring about replacing minor league players. I apologize again for the very fluid nature of the minor league roster rules and process this year. We will eventually benefit from all the back-and-forth discussion this first year of adding minor leaguers.
The reference to replacing players appears in the section titled "What happens during the season?":viewtopic.php?f=23&t=18471&p=139671&hilit=minor#p139671