The Gibbs-White one was the biggest blow for me and has caused the most damage. There is a massive hole there that so needs filling.
Bentancur is clearly being miscast in filling that role, given he just isn't the player from Conte's time thanks to Twatty Fash Of course, the loudest members of our fanbase insists that Eze was the biggest blow, somehow failing to comprehend that it doesn't matter if Eze or Simons or whoever is at the tip of our midfield if the pivot isn't getting the ball forwards
He would have been ideal but like HBIC says, there should have been a plan b. Don Fabio must have been able to find someone in Italy who could have been a back up.