It's really hard for Ruben Amorin because he can't prove himself as a great coach worthy of being at Sporting CP they are at the club now much more complicated and certainly will be more pressure, especially next week against Liverpool as away then they will be difficult to win and this will continue to approach the relegation zone.
Chelsea's defeat is still good because they are in the top half of the table, this is not too bad, meaning that the UCL qualification competition is still there for Chelsea, while Manchester United is still a long way to return to the right path.
In as much as Manchester United are experiencing difficulties, it doesn't mean that Ruben Amorim is not a good coach. Manchester United are in transition and it takes time for a team in transition to balance and be able to find their rhythm and get back to winning ways. Though Manchester United might be struggling now and are in the bottom half on the standings, I am very confident with Amorim as the head coach, he will surely navigate them out of their present situation and bring them back to winning ways again.