3. William Saliba looks fatigued
Playing every minute of every Premier League game is starting to show on Saliba. There were even a few warning signs of his fatigue during the otherwise stylish 5-0 beatdown of Burnley.
Saliba appeared similarly off the pace against Porto. He was static when the hosts swept forward in a rapid counter attack Galeno inexplicably wasted with a pair of shocking misses in front of goal.
Arsenal had a fortuitous escape, but this was far from the only time Saliba was caught out by Porto's pace on the break. He appeared unprepared for the powerful running of Galeno and lone striker Evanilson.
Saliba isn't going to become a liability overnight, but he is a player in need of whatever breather Mikel Arteta can provide him.