Manchester United fans have hailed Kobbie Mainoo’s stunning performance against Newport County in the fourth round of the FA Cup on Sunday at the Rodney Parade. Kobbie Mainoo has had a remarkable breakthrough season at Old Trafford and has firmly established his place in Erik ten Hag’s first-team Manchester United squad. The 18-year-old midfielder missed the opening of United’s season after he picked up an injury in pre-season before making his Premier League debut last November. Mainoo earned rave reviews for his performance against Everton in the 3-0 win at Goodison Park and has since become…