Yep, no decent cover at CDM or RB/LB has cost us dear and we're yet to see what happens at CF if Erl gets crocked now Alvarez has gone.
But how risky was it not to have cover at CDM? Until his current injury, Rodri was an absolute machine, who has almost never been injured. If the defence is ok, then Kovacic (and even Gundo on the odd occasion) are capable of deputising.
At RB/LB, Walker/Lewis/Stones and Akanji have all played right back without major issues. Ake and Gvardiol have played left back, and Akanki and Rico can play there in a pinch.
What's made the team successful for the last few seasons, is players being given regular minutes, and that adaptability. Going the United way, and having expensive players that you forget are even at the club just in case isn't exactly an example to follow.