it's certainly possible. Reed should be able to recite Rex's defensive playbook.
Reed also played for Dennis Thurman in Baltimore, so a lot of the calls are probably familiar to him.
But you have to realize that he spent multiple years away from this staff and he just learned an entirely new scheme in Houston.
It should be easy for him to pick back up, but it may not come right away.
Schemes are going to change. You will get destroyed if things stay exactly the same.