Manchester United will never go on relegation no mater how poor their performance is. However, most people sees Nottingham Forest as the favorite in this match because, they have been doing pretty good since the beginning of the season. On the one hand, Arsenal might find it difficult to win Fulham because Fulham is a team that accepts defeat easily.
I agree, as bad as the squad Manchester United have, it's not enough to make them enter relegation zone. They need two thing, bad squad and point deduction. Nottingham Forrest looks better than Manchester United, they perform well against Brighton in FA Cup.
If you said Fulham accepts defeat, it means Arsenal will easily win the match.
Arsenal will win in this match, just like how Crystal Palace humiliated Fulham.
Manchester United United is on the 13th position in the English Premier League Table so I also doubt if they will enter the relegation zone. They are not bad as to enter the zone. And they will join the Europa League and clubs like Southampton, Leicester City and Ipswich Town are already in the relegation zone. On the 2nd of April, Premier League will resume again and you can see the fixtures here.