Stepping into an undesired role is never fun but it's necessary. In order to become the player you want to be, you have to be willing to do what's best for the team.  If this means coming in and playing a lock down defender, be the best defender a coach could ask for. Build a coach's trust and they will allow you to step into the role you want.  

Here are some great resources: 

https://pgcbasketball.com/is-pgc-right-for-you/

https://www.youtube.com/channel/UCBopgKE8I0CHtd4490NeWNQ

https://jordanlawley.com/tgs/