They do not necessary have to be a reshuffling because the coach can use the same playing style that the previous coach used with some little adjustments and he can get a good feedback from the players. What is important in coaching is the mindset that you set for the players to use when playing a serious game. The previous coach did not have a good mindset for the players, he always gives them an average fighting sprint and when the players are losing, they can not comeback to win the game because the coach has not made that a part of their training. The new coach should not make toon many changes to the team or they will have to start all over again and this is when they will have some challenges as they will have to build a new relationships from the start.
I was not surprised since Pochettino couldn't get good results in Chelsea as they wanted to see while he spent too much money on this team. I think he is even expecting to see this coming up for him in Chelsea because of the performance he had during all these games.
But the good point about Pochettino was about using younger players. He tried to get rid of the older and expensive players in this team by putting some of them for sale and instead, Pochettino bought many younger players for Chelsea to have a better team.