In association football (soccer), a defender is a player who tries to prevent the other team from scoring.
There are four types of defender - centre back, sweeper, full back, and wing back.
Centre backs are often tall, with good heading and tackling ability. An ability to read the game well is a distinct advantage. Sometimes, particularly in lower grades of football, centre backs concentrate less on ball control and passing, preferring to merely clear the ball in a "safety-first" fashion. However, there is a long tradition of centre backs having more than just rudimentary footballing skill, enabling a more possession-oriented playing style.
The position was formerly referred to as centre half, although the emphasis of the centre half was more forward thinking in action. In the early part of the 20th century, when most teams employed the 2-3-5 formation, the two players at the back were called full backs and the row of three players in front of them were called half backs. As formations evolved, the central player in this trio, the centre half, moved into a more defensive position on the field, taking the name of the position with them. The right and left players in the trio were called the right half and left half respectively.
Centre backs usually remain in the half of the field that contains the goal they are defending, but tall defenders will often go forward to the opposing team's penalty box when their team takes corner kicks or free kicks, where scoring with one's head is a possibility.
Some sweepers move forward and distribute the ball up-field, while others intercept passes and get the ball off the opposition without needing to hurl themselves into tackles. In modern football, its usage has been fairly restricted, with few clubs in the biggest leagues using the position.
A relatively recent innovation is the "Sweeper-Keeper" where a goalkeeper stays higher up the pitch than he might normally do, and performs the defensive actions of a sweeper by clearing long and through balls outside the penalty area. Most of these goalkeepers are fast and with some outfield skill, required if they get themselves into trouble with a poor decision to "rush out" of the penalty area. Many of these keepers are also "eccentric" which can sometimes combine to cause disastrous mistakes such as losing the ball outside the area to an opposing striker, handling the ball or fouling and being sent off or being lobbed after being too far out of the goal area. This style is considered to have developed as a result of the new back-pass rule in 1992.
In the traditional 2-3-5 team formation, the two players in the final row of defence before the goalkeeper were referred to as full backs. This formation is little used in the modern game, having been replaced largely by the four-man defence, but the term "full back" lives on — the full backs now occupy the wide positions in the defensive line, with the old centre half [back] doubled-up to fill the central defensive position.
The traditional English full back was a large, strong man who would make substantial use of "hacking" - deliberately kicking the shins of opponents, a practice that was accepted as legal in Britain but not in other countries, and caused major controversy as the game became increasingly internationalized from the 1950s on. It is now effectively banned everywhere, and it is this in part that has given rise to a different set of defensive roles.
In contrast, the role of the full back often involves an attacking element: to some extent the full backs have replaced the winger and are expected to get forward to deliver crosses from a wide position. The modern full back is usually pacy, strong in the tackle and with good stamina to get up and down the field.
In the evolution of the modern game, wingbacks are the combination of wingers and fullbacks. As such it is one of the most demanding positions in modern football. Wingbacks are often more adventurous than full backs and are expected to provide width, especially in teams without wingers. A wingback needs to be of exceptional stamina, be able to provide crosses upfield and defend effectively against opponents' attacks down the flanks. A defensive midfielder is usually fielded to cover the advances of wingbacks.