Well to be honest the problem with Poulsen is not that he is bad. He actually scored twice in a season! Something Tiago couldn't do in a 3 years and won't do for atleast 20 more years at this rate.
The problem is that we have waaay too many DMs. We have him, Tiago, Zanetti, Sissoko and now even Melo. There is nothing to lose from selling ANY of the lesser used DMs and the money could be spent on investing towards areas that need it (in short, the back-line)