Retired jersey numbers

Hey guys, is there a way to unlock/use retired jersey numbers?

There's an easy way to get around it in the in-game edit player screen. Temporarily change the player's name to the person who has the retired number. You'll then be able to select that number. You can then change the name back, and the number will remain.

is this method would work in My Career?

No, only when editing/creating a roster.