#4 Injuries changed the complexion of the match

Arsenal had to start the game with 7 first team players injured, at least 3 of whom would have definitely started the game had they been fit. Arsenal fielded Maitland-Niles in the spot usually occupied by Hector Bellerin, and though he does have a similar level of pace, all the other areas of his game are far behind the Spanish fullback, who was sorely missed tonight.
Granit Xhaka had to start at CB to cover for the injured Rob Holding and Shkodran Mustafi, and he was uncomfortable in his unfamiliar role, having to be bailed out by Monreal, Cech, and Sokratis on several occasions.
Arsenal's board must have noticed how badly stretched the squad is and the real lack of depth compared to other title rivals, and must recruit accordingly to help the coach execute his gameplans better.