From Moyes description it sounds like he wants him to play like a Lampard/Cahill deep lying striker sort of midfielder. They've no shortage of passers and tacklers in midfield and are quite good at controlling games, what they lack in abundance is goalscorers and I suppose since Cahill stopped performing that may be the root of the problem. I'd imagine he sees him as the successor to Cahill unless the departure of Rodwell or Felliani is imminent.