Any way to prevent teammate trades on Mycareer?

[Juta]

This is just so frustrating. First I lost dirk nowitzki. Then I played 1 whole season to get him back. I suggested him along with other 4 unrealistic ones but then no trades happened that season! So that means it's possible to prevent trades or it only happens after your first season? Because I started a new career and I don't want my team to be changed so I suggested the top 5 players (james,rose,durant etc) but shit the trade still happened!