Arsenal and Manchester City now lead all 92 clubs in the English football pyramid when to comes to one stat. Arsenal have been incredibly solid at the back this season. The Arsenal defence has been in a class of its own this season. No side in the Premier League has conceded fewer goals this season so far than the Gunners, who have only had their net breached on 24 occasions in 28 league matches. What makes Arsenal so good at the back?There are several factors that have come together to make the north London club such a difficult team for opposition sides to break down. William Saliba and Gabr…