I think with Meireles & Lucas in the midfield, Poulson is their just to defend the back four, I'm sure he won't do any runs upfront, he may not even pass the midfield line, so when we have the ball, Kelly & Johnson go to their forward runs, Poulson returns with Agger & Skrtel in the back.
A little bit like how Busquets operate at Barca is that he drops deeper to be in line with Pique & Puyol with Alves & Abidal pushing up.
Or so me hopes.