Question: Do defensive positions differ from offense?
About the article "Water polo", section "Defense".

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The defensive team or defense is the team that begins a play from scrimmage not in possession of the ball.
The object of the defensive team is to prevent the other team from scoring.
The defense accomplishes this by forcing the offense to turn the ball over, either by preventing them from achieving a first down and forcing a punt, or by forcing the offense to fumble or throw an interception.
Unlike the offensive team, the rules do not restrict the defensive team into certain positions.
A defensive player may line up anywhere on his side of the line of scrimmage and perform any legal action.
Over time, however, defensive roles have become defined into three main sets of players, and several individual positions. 
The wheel offense is very advantageous to use.
First it is very flexible and easy to set up.
All the positions in the wheel offense are interchangeable (i.e.
the point guard doesn’t have to be the first cutter).
This enables the ball-handler to start the wheel offense from either wing without the other players changing their positions.
With its flexibility, the wheel offense blends well with both half-court attack and fast break.
Once the play is set up, the wheel offense can work effectively against both man-to-man defense and zone defense.
The various cuts and double screens will create open shot opportunities if the defense fails to react quickly.
Even if the defensive players manage to cover all the cutting offensive players, they are forced to switch match-ups.
Switching match-ups often causes mismatches between offensive players and defensive players, and when mismatch happens, the offensive team often take advantage of it to score.
Also, when a team runs the wheel offense, their game tempo will be very hard to disrupt.
The wheel offense can also integrate other offensive plays.
Pinholster's Oglethorpe team would often run some concealment plays before they start the wheel offense.
This made the wheel offense very hard to detect, and they could catch the defense off guard.
During the play, when the wheel offense is in the 1-3-1 formation, it can also switch to other plays based on the same formation.
This greatly increases the variation of the wheel offense, making it very hard to defend.
Moreover, the wheel offense is very helpful for team-building.
Because the wheel offense demands every player to have good ball-handling and shooting skills, each player is forced to develop more fully.
In the wheel offensive play, five players play as a team rather than individuals.
Thus practicing and running the wheel offense is very helpful for developing a team spirit among the players. 
Defensive strategies differ somewhat from offensive strategies in that, unlike offenses that have very specific, detailed plans and assignments for each player, defenses are more reactive, with each player’s general goal being to “stop the offense” by tackling the ball carrier, breaking up passing plays, taking the ball away from the offense, or sacking the quarterback.
Whereas precision and timing are among the most important parts of offensive strategy, defensive strategies often emphasize aggressiveness and the ability to react to plays as they develop.
Nevertheless, there are many defensive strategies that have been developed over the years that coaches use as a framework for their general defense, making specific adjustments depending on the capabilities of their players and the opponent they are facing.
Some of the most commonly known and used defensive strategies include:  Man-to-man  Coverage shells (cover 2, cover 3, etc.)
Zone blitz  Tampa 2  “46” defense  5-5-1 Two-level defense  
The goal of defensive strategy is to prevent the opposing offense from gaining yards and scoring points, either by preventing the offense from advancing the ball beyond the line of scrimmage or by the defense taking the ball away from the offense (referred to as a turnover) and scoring points themselves. 
In sabermetrics, the defensive spectrum is the graphical representation of the positions on a baseball field, arranged from left (the easiest defensive positions) to right (the hardest).