Fellaini was red carded during the midweek draw with Real Sociedad and has still to score for his new club.
Yet Moyes believes there is an explanation for the Belgian's slow start.
"We had to put him in earlier than we thought," said Moyes. "He was a little bit behind and my plan was to put him in much slower and give him a chance to settle in.
"But we had to put him in and he wasn't quite ready.
"I actually thought he played well in Sociedad.
"We could have taken him off after the first booking but given how close the referee was to the incident he must have got it right."
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