A back is a defender.
Neelanjan LakshmanPique
Yes, if you are a defender.
defender
Pressure of the defender
Defender...
a defender that is on the right side
John Terry of Chelsea and England.
goalie, defender, midfielder, forward
Today it is the Brazilian Danny Alaves.
Defender or Midfielder
The defender usually depends on the sport. In soccer (football) the defender is the one that protects the goal. I don't know much about football (American Football)