One Manchester United player has been criticised for his “poor” performance in the derby defeat against Manchester City on Sunday.Man United were humiliated by their fierce rivals at the Etihad after Erling Haaland’s brace and an early goal from Phil Foden, which piled the pressure on Ruben Amorim.Too many Red Devils superstars have been savaged by pundits and supporters alike for their below-par displays this season, and the same names were found wanting again at the weekend. Click to subscribe to the podcast Club legend Rio Ferdinand is no stranger to big games and he was left with a sour taste after watching United capitulate, singling out one big player for being especially bad.Photo by Nigel French/Sportsphoto/Allstar via Getty ImagesRio Ferdinand says Luke Shaw was ‘poor’ and reacted ‘too late’ in Manchester derbyLuke Shaw has been a loyal servant since arriving at Old Trafford from Southampton in 2014, but he has been accused of not being good enough to perform in a demanding 3-4-2-1 shape.The 30-year-old has been ousted from his usual left-back position and moved into a back three in a tactical error, which has also led to another Man United player looking ‘lost’ in Amorim’s system.That meant he was asked to shackle Haaland, a task he never got to grips with, and Ferdinand believes he just wasn’t sharp enough to react before the City striker could do damage.Speaking on the latest episode of Rio Presents, he said: “But in the derby, he just isn’t sensing the danger. He’s not covering the other players. He’s not getting his arms across his body to block Haaland. He’s reacting too late – he’s not smelling danger at all.“When I look at it, I don’t think it’s a system issue. Take that goal, for example, where [Nico] O’Reilly nutmegs someone, pops it around the corner, and runs to the other side – and suddenly it’s through for Haaland. “That’s great football; you sometimes have to say in the midfield area it’s great football. But defensively, from a Luke Shaw standpoint, I thought it was poor, and it could have been avoided. I just think there were too many defensive mistakes – we got opened up far too easily.”However, Ferdinand wasn’t the only Man United great to tear into Shaw.Photo by Carl Recine/Getty ImagesRoy Keane says Luke Shaw is ‘getting away’ with things at Man UnitedThe defender was arguably at fault for all three City goals. He had stood off Jeremy Doku before he crossed for Foden to score the opener, and was then outmuscled by Haaland for City’s second. Capping off a day to forget, Shaw lost the ball cheaply and was out of position, allowing Haaland to burst through United’s entire half before beating Altay Bayindir.Speaking on Sky Sports, Roy Keane did not hold back in his assessment of his performance.Keane said: “We see Shaw for the first goal. Shaw is an international footballer, for him to get caught out like that [is not good].StatisticTotalMinutes played90Touches66Tackles1Blocks0Recoveries5Dribbled past1Luke Shaw’s stats vs Manchester City – Fotmob“I think Shaw has been getting away with murder for years at United. Always injured, never quite fit, and we make excuses for him.“Then he gets a few games under his belt and he’s making decisions like he doesn’t want to tackle people.”Clearly, it’s time for Amorim to either drop Shaw or swallow his pride and finally change to a back four, which would bring out the best in the full back. He hasn’t become a bad player overnight, but too often, he has been exposed by the system. A big decision must be made ahead of this weekend’s must-win showdown with Chelsea.