maybe this could help someone.. after clicking on MC-change to this player, my MC character actually changed teams. Allow me to clarify:
First I did this:>Created Player (the one i want to use on Mycareer) I put on The Hornets.
>started Mycareer, finished game, got drafted by Brooklyn Nets( my team of choice.)
Then I followed these steps:
"Okay, let's start.
1. Load your preferred roster and go to "Options" > "Manage Roster" > "Rosters" and edit your preferred player that you want to create for MyCareer. Save all changes. Or you can change nothing and leave everything by default. From main game screen go to "Features" > "MyPlayer" > "Edit MyPlayer" and set the skintone and any name ("Lol Lol" for example), it doesn't matter.
2. Start new MyCareer. Play (or skip, use trainer option) Rookie Showcase. Go through the Pre-Draft interview. Get drafted by any team except the one which there is your preferred player. For example, if you want Paul George - don't get drafted by Pacers, want D-Rose - don't get drafted by Bulls, ect. Save all changes manually. Close the game and start it again. Load your MyCareer save file.
3. On main MyCareer screen (it's where calendar, tweets, your minutes, ect.) you minimize the game and start the trainer. Push LeBron icon (screenshot) "1.", search your preferred player by name (screenshot) "2.". Right click on his name - it call the pop-up menu. Click on the last line of this menu (screenshot) "3.". Maximize the game and save all changes manually."
after which, My player changed to the one I put on the Hornets, and i also changed teams. Got drafted by the Nets but after steps 1-3, was able to change into the player of my choice, along with the team I put him on, which is the Hornets.
Hope this helps someone wanting to change teams in the future on MC mode.