My brother rates Fellaini as the least talented player he ever saw for united. I would dispute that but Moyes just had him run around kicking people and never played to his strengths except when putting him up top to knock down headers.
He told me of one home game where Fellaini once got the ball at his feet in midfield and had no idea what he was supposed to do. In the end he held it up as long as he could and passed it out for a throw in... David Moyes ladies and gentlemen
I still maintain that Fellaini going to United at that time wasn't a bad buy as a jack of all trades. Throw him on with 20 minutes to go and he can play defensively and can cause mayhem up front if they were chasing a game. A rugged style, but effective for a team at the very top who need an extra dimension to their play that they wouldn't normally use. The big thing was not refreshing the players who should be starters. Anyway, yesterday's news and yesterday's man.
Having him to throw on as a last resort (when actual football isn’t breaking down a stubborn defence) is not a bad option to have. Problem is he was not a last resort. He was integral to the Moysie way, the non footballing way.
Often a manager will have a player that reflects his managerial style, for example Roy Keane was regarded as “Fergie on the pitch”. They share many characteristics (in this case, driven, take no prisoners, inspirational, fight to the end, winner). Fellaini was just such a figure for Moyes. Plenty of graft, no style, ugly to watch, and devoid of success.