The red card issue actually destabilized the entire game plan for Chelsea, from the replay of that tackle, and if it were to be some referee they might have considered that tackle as not a red card offense but should have been decided as a yellow card offense rather, the tackle in my opinion was not that intentional as they offender went for the ball first before matching on the opponents leg. Anyways, performance was bad and Chelsea did have ample opportunity to have gotten a goal but they couldn't utilize any.
Pochettino might as well count his days as headcoach of Chelsea because his clock is ticking, the supporters keep echoing and chanting about his sack during games at Stamford Bridge. Losing 1 nil was a dissapointing results for the blues, they never expected a red card for the defendlines. Malo Gusto tackle was probably based on gaining the ball, but with irrelevant raising up his boot towards his opponent, making it everything clear as a deliberate action. Chelsea previous game against Aston Villa, experiencing defeat was not part of the plan, instead they would have settle for a draw tie.
I agree with you and I think Pochettino as well knows that with the way things are going with Chelsea he may not longer be incharge of the club if Chelsea don't experience a positive change from now till end of September. Not only the supporters of Chelsea are chanting for him to be sacked but the players also are being fed up playing under him because it seems their performance can't improve under him and I see no confidence in him again as the head coach of Chelsea.