He plays as a reserve and comes off the bench.
In Rugby Union (15 a-side, as opposed to Rugby League which is 13 a-side), the number 9 shirt is worn by the scrum-half
I believe it was number 7
15
Usually number 8
A player with 12 on their jersey in the Union code will play inside centre in the backs line (stands with another centre outside them and a flyhalf the other side)
Hes an open side flanker number 7
Number 22 in rugby is a player on the reserves. Therefore it could be occupied by a player of any specialised position. However, the player in number 22 is usually an outside back utility(playing centre, wing and fullback)
The number is normally associated with the players playing position
A Rugby jersey.
Silk
England