Graeme Souness has suggested that Erik ten Hag made a mistake by allowing David de Gea to leave Manchester United. Erik ten Hag opted for a change in the goalkeeping department over the summer as David de Gea left Old Trafford. The Spaniard reportedly failed to agree terms on a new contract, with Manchester United then moving to bring in Andre Onana. It’s fair to say that Onana has endured a shaky start to life in Manchester following a brilliant campaign at Inter Milan last time out. And Graeme Souness believes United didn’t necessarily have to move De Gea on for Onana last summer. Souness sa…