If you take the season as a whole we can live with Sergio missing games, we had a slow start (away from home) and a dip in Feb, but the season is long and hard and there are still games to be won, I cant believe this is being raised.
Just look at the other clubs in Prem and if Chelsea lost Hazard they would be struggle badly , if Liverpool lost Suarez they would have dropped points, we have not done too bad without him, but we can still call upon him in last few games.
How would United go on if Fellaini missed 10/12 games(I know I am being silly now).