A little analysis from me. Chelsea's mistake against Arsenal was that they were too confident that they had won against Arsenal from the 60th minute. Even though Arsenal were hotter this season when Arteta replaced players in the second half, and that is Arsenal's strength this season.
Everyone didn't believe Arsenal would be able to equalize in the match. Pochettino also had the confidence that he had won the match already, but Arsenal was able to equalize in the match. Pochettino shouldn't have substituted Sterling and Palmer in the match, he should have just let them complete the match. But even the draw is not a bad one for Chelsea, playing draw against Arsenal is not really easy. Everyone was expecting Arsenal to win the match with a wide goal margin, but it ended in a draw. The draw really affected Arsenal because Manchester City is now ahead of them on the table again.
Advice for Poch, don't be careless in changing players, even the tempo of the game.
I am sure Pochettino will have learned his lesson, and I am sure he will avoid similar mistakes in the future. It's a good idea to substitute some of your key players towards the end of a match when you are winning comfortably, but it shouldn't be with a club like Arsenal. We all know Arsenal to be a dangerous club. He should have just maintained the players he started with, but this will serve as a lesson to him.