Herrera - 39 appearances (11 as sub though) mainly in AMC - 4 goals 2 assists
Pjanic - 41 appearances (3 as sub) mainly in CM - 12 goals 12 assists.
Surely there is a fair difference there mate? At Roma he is probably their player of the season, him or Salah, maybe Florenzi I'd say
I've watched plenty of Roma and United this year. I like Herrera, I'd like to see him start a good run again but anyway, he's AMC.
In CM you will probably be losing Carrick. That leaves Schweinsteiger and Schneiderlin as the main CMs with others who can play there like Felliani, Hererra or Blind. Schweini still needs to be starting consistent games, he's your DLP.
None of these are going to score or assist a great deal but I think the team would benefit from a CM who does chip in goals and assists. Of course it will probably fall to the fact LVG wants ball retention and players sticking to certain roles which is why no CM is involved in goals this season. So a change of set up would probably rectify that as you certainly have players that are capable of much more.
They don't necessarily NEED Pjanic, but having him would be one **** of an option. Still, he would be expensive....