MANCHESTER UNITED’S hierarchy are still behind Ruben Amorim despite another disastrous day in the derby.The Red Devils were thumped 3-0 by Pep Guardiola’s City at the Etihad – meaning they have just four points from four matches.GettyRuben Amorim has come under fire[/caption]That is their worst start to a Prem season since 1992 and they also crashed out of the Carabao Cup to League Two Grimsby last month.Amorim said afterwards he will not change his 3-4-2-1 system – despite concerns it is not working.He added the United top brass will have to replace him if they do not feel it is the best way forward.However it is understood the board remain calm and behind the former Sporting Lisbon boss as well as being willing to give him time to get things right.Part owner Sir Jim Ratcliffe was pictured with his head in his hands during a difficult day at the Etihad.The Ineos magnate sanctioned a £220 million summer spending spree for Amorim over the summer.And sacking the 40-year-old Portuguese now would just mean another rebuild is needed.Amorim has taken just 31 points from the 31 matches since taking charge at Old Trafford in mid-November – losing 16 of them.BEST ONLINE CASINOS – TOP SITES IN THE UKShutterstock EditorialSir Jim Ratcliffe couldn’t hide his frustration up in the stands[/caption]That is the lowest points tally of any of the 17 clubs who have been in the top flight across both seasons.They finished 15th last season and their Europa League final defeat to Tottenham means there is no European football for only the second time since Sir Alex Ferguson retired in 2013. Amorim knows the pressure will continue while the results are not coming.He said: “It is not a record you should have at Manchester United. You have no idea happened during these months – there are a lot of things.“But I accept it and I am not going to change.“When I want to change my philosophy, I will change it. If not you have to change the man.“I believe in my way and I will play my way until I want to change.”United have another tough fixture looming with world champions Chelsea arriving at Old Trafford on Saturday evening.PAMan Utd are 14th in the early Prem table[/caption]