The old guard is the biggest problem at the moment, think some of them still want Pep as manager. Trouble for them is that even if he did come back (extremely unlikely imo), they couldn't play at the tempo he would want. Also, deep down Koeman knows he is probably only keeping the seat warm until a new President is elected, and the players know that too. Defensively they are shambolic. Even at their peak they weren't the greatest, leading to some CL horrors, but they got away with it for the most part then because they were so good in possession that they were never under pressure for long. Now that they can't keep the ball at the other end of the park, the defence is getting shown up.