A couple of years ago, Arne Slot could savour the sound of Anfield in May. It was Jurgen Klopp , chorusing his successor’s name in a gesture of generosity. Two years on, the noise was less welcome, if unsurprising to the only other title-winning Liverpool manager of the last three decades. There were boos twice: first and loudest when Slot substituted Rio Ngumoha , then at the final whistle as his side had laboured to a 1-1 draw that ended Chelsea’s six-game losing streak. Individual incidents form part of a wider pattern, and the broader picture of discontent, the readiness of the Liverpool faithful to make their unhappiness audible, should concern Slot more. Ngumoha had cramp, the Dutchman reported, and the fans were not to know that. But his removal should have been no surprise, given that the 17-year-old is yet to complete a game in his senior career, and a crowd-pleaser has become a lightning rod. Slot expected the boos because they tend to come with Ngumoha’s withdrawal.…