Even against a championship team, Chelsea was so overwhelmed and lucky they were still able to win until the final minute of the match. Leeds played very well because they managed to put pressure on Chelsea from the start and even if Chelsea finally conceded it wouldn't be a surprise. The match ended with a score of 3-2 for Chelsea's victory in the FA Cup match and both teams did not proceed to extra time.
A standard match for Chelsea in recent times, when after a defeat, they then beat a Championship team in the FA Cup. Although it should be noted that Leeds are in 2nd place and are fighting for a place in the EPL, so it can not be called a weak team. The match was quite boring and we can say that the second half Chelsea played quite badly and if not for Gallagher's goal, it is unclear how things would have turned out in the end for Chelsea.
This season the management gave Pocchetino the opportunity to experiment and you can see that he is trying to pick the optimal lineup, but unfortunately it does not always work out and very often Chelsea even in one match can play great one half, and the second half to play as if it is a different team.