My position is linebacker.
Linebackers are defensive positions in football. How long have you played football? 
I have been playing since I was 6.
So how many years is that? American football positions have changed over the history of american football. 
That would be 25 years.
Have you ever played rugby? American football and rugby have many similarities. 
No I have not.
The earliest history of football can be traced rugby football.