[Ike348]

Here is what I have done in some of my fictional leagues. First, I created a new MLB league and deleted all of the players I didn't want to carry over to my fictional league. Then I exported the rosters, and imported them into Excel.

Next, I created fictional FAs (must be in commissioner mode) that matched the number of MLB players I was carrying over. Then I exported those rosters.

For the MLB rosters in Excel, I changed the player IDs to match the fictional FAs IDs. I then exported the MLB rosters to a CSV, and then copied the player portion of the file (not the list of teams). I then selected all of the FAs in the fictional league file and pasted over the MLB data. Then re-import the rosters into your fictional game. Your FAs should now be all real MLB players!

Note that this does not include statistical history, but you could copy that over much the same way.