Mertersacker wasn't all that good for Bremen to be honest, they were happy enough to sell him on, he had half a decent season for them but wasn't so good for most of the rest of the time.
Vermaelen had half a season where he galavanted forward and got onside with the fans by scoring a few goals, other than that he's been hopeless.
They're both average players, throw in Koscielny the calamity and you start to realise our defensive players would be better suited working in a circus.
If we want a decent defence we need to scrap these clowns and bring in some quality players who know how to defend and have the attributes to make a good backline.