I think the idea that we work harder than other PL teams is a total myth. When you look at average or overall distance covered, the difference between teams is negligible and although the most recent data I could find was from a month ago, we aren't even in the top 3 of overall distance covered. That goes to B'mouth, Brighton and Brentford.
However, the same data showed that we are top for overall sprints:
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This, I feel, is where the real fatigue problem lies. The system demands sprints, but only from specific players. Mostly the back line, but the forward line also takes a huge brunt of it as they are constantly sprinting to achieve the high press.
The strain on those two areas is obvious. If you were to plot our injuries over time under Ange on a graph and categorise them by position, the overwhelming majority belong to our defenders or attackers. Even Bentancur and Bissouma who both had extensive injury issues before Ange joined and at previous clubs have been surprisingly injury free (notwithstanding contributions by Twatty Cash) since. Kulusevski hasn't had a single injury under Ange, despite missing a chunk of games under Conte/Mason. Sarr has had one minor knock and Maddison hasn't had one since the Chelsea game last year.
The point isn't that the midfielders need to work harder to ease the strain on the other areas. The system is designed so that the entire back four is regularly 40 yards out of position and needing to sprint to get back. It is designed so that the 3 attackers need to tirelessly chase the ball across the final third. The system is similarly designed so that the midfielders aren't meant to spring much at all - that is the whole point of a high press, that the midfield's zone of operation shrinks from 100 yards to 50.
What we need is more quality there. Players who lessen the workload on others by simply doing more to control possession and dictate the game. The level of quality in our passing that I am watching on a regular basis is poorer than anything I can recall in recent years. Even simple passes are going straight to opposition players or straight out of play. If the former happens and the opposition are useful with the ball, that triggers a need for multiple players to sprint back like mad to get back in the shape.
All of Bissouma, Bentancur, Maddison and Kulusevski can be significantly upgraded imo. I've been banging on about it all summer and all season, but I was staggered that we prioritised spending money on more attacking players when last season showed that the midfield is a chronic problem. Archie Gray and Lucas Bergvall are potential upgrades for years down the road. Here and now, the midfield is the team's weak link and it is killing the whole system as a result, leading not just to defeats but to injuries too.