Chaotic and, at times, shambolic deadline-day dealing ended with Fellaini being United's only significant acquisition.
And at ?27.5million, the 25-year-old has not come cheaply.
Indeed, Moyes' decision to let a clause in Fellaini's contract expire at the end of July backfired as it ended up costing United an additional ?4million, turning the Belgium international into the fourth most expensive purchase in the Red Devils' history.
However, having worked with Fellaini for five years at Goodison Park, Moyes is acutely aware of the former Standard Liege man's qualities.
And he has no doubt Fellaini will thrive in his new environment.
"Marouane is not someone you want to be playing against," Moyes told MUTV.
"He has attributes other people don't have. And with those qualities he has, I am sure he will be a big player for Manchester United."
Moyes will be relieved to bolster his midfield options.
The Scot identified it as a problem area as soon as he took over from Sir Alex Ferguson in July.