I know what you all mean, but if they don't score, arn't they subject to a counter-attack?
---------- Post added at 02:14 PM ---------- Previous post was at 02:13 PM ----------
And most defender goals are from set pieces anyway...
Yes, most backs do score from set pieces but open play goals are not as rare as you think, and especially if it is a fullback. I remember seeing Sol Campbell sink a devastating 30-yarder against Portsmouth from open play a few years back. Sol Campbell actually started his career as a striker. In some cases, in real life, if a game is tied or you are heading for a defeat by a goal, a manager will send one of his centrebacks into the attacking line and use his strength and heading abilities as a target man on the end of long balls into the box.
In all cases, as mentioned, the midfielders will be aware of this and one will pick up the slack by dropping into the void created by a roaming defender. If a fullback attacks, the wide midfielder/winger will hang back and essentially fill in as the fullback. Gary Neville and David Beckham were famous for this. Neville would regularly overlap Beckham and Beckham would sit on the halfway line, ready to deal with a counter attack down the right flank. If a central defender picks the ball up and moves forward, a central midfielder, usually the more defensive minded one, will drop back into the role of the centrehalf. These are professional footballers. They are aware of what is going on. A winger won't just race off if his fullback overlaps him as he will be aware that the entire side of the field he has left will be unprotected.
And anyway, attacking corners, when the centrehalves do go forward, often see counterattacks succeed and that is a pre-determiend move when the entire side is prepared. Yes defenders don't spend 90 minute in the oppositions half, but they do push upfield, sometimes sitting as high as the halfway line and they will go forward. You'll also sometimes see, if the tempo of the game drops, a defender may be the one that makes a run from the back to try and create a spark. Some defenders, like Sol Campbell, with experience as a youth striker will often bomb forward.
Campbell's driving run and long range effort against Portsmouth:
http://www.youtube.com/watch?v=77XsFYMmGug
Watch this run from Tony Adams. He leaves the line and picks up a lobbed pass and finishes. The awareness, the timing of the run and finishing here would make most top line strikers proud:
http://www.youtube.com/watch?v=un43ZP3aiS0&NR=1