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.
Comparison of American football and rugby union
A comparison of American football and rugby union is possible because of the games' shared origins, despite their dissimilarities.
Rules.
Rules Tackle.
In the event of a tackle in rugby the player may pass the ball behind him provided he is not on the ground. If the tackled player is on the ground, the ball must be released, allowing any other player (including the opposition) to pick up the ball (usually a ruck forms) and the play continues
of the same position. The positions were later renamed "linebacker". However, that did not become the usual way to name that position until platoon football became common, with players specializing in offense or defense, substituted according to which team has the ball. There seems to have been some tendency for defensive positions to be named for where the player would play on offense, although quarterback and safety formed an early exception.
When linebackers are playing close to or level with the line, a somewhat reliable way to distinguish