Well, the OP is suggesting that we're not as bad as we think we are, and the same problem afflicts other teams. This may be true, because obviously we don't pay as much attention to what happens with others teams, but all I know is that when we get a corner I usually feel we might as well just give the ball to their goalie and carry on from there.
Don't think we're quite as bad as we make out, although it's clearly not our strong point. Toure & Sakho obviously add extra quality when defending set pieces at the back. Skrtel is good at attacking them and which ever way you want to look at is is good at defending (rarely let's his man get a free header) but bad because he's always susceptible to giving away pens with his rough handling. Agger is probably our worse CB, no only is he not the greatest in the air (not a huge complaint as his attributes in other areas are better) but his man marking is terrible, from set pieces and open play. Small movement easily beats him. Gerrard's delivery from free kicks is 2nd to none, however I think he tries too hard to get whip, bend and get the ball up and down which is why so many either hit the first man or go way over. When he does get them right they are very good though (see Skrtel's header v Fulham). It's one of them things were we all would like to see us do something different, but when you **** up a short corner, everyone moans and says what a waste, why not stick it in the box for the CB's to attack!
