Brendan Rodgers has thrown down the gauntlet to Mikey Johnston after the Celtic winger got his first start of the season against Hibs last night. The 24-year-old Republic of Ireland winger got the nod after his impressive substitute showing against St Johnstone and, overall, he did make an impact. However, it wasn’t enough. According to the Celtic manager, Johnston needs to improve further if he is to get a regular starting place at Celtic this season. Rodgers said [BBC Sport Scotland], “Mikey needs to do more, that is the reality. He has big talent and comes into the game but if you are going…