I have said it on a chat.
I hope that someone will make a Gif or something.
Dembele left his player alone two times.
He was near the player around the box, then Dembele looks at the action on the other side of our box and forgets his player.
Then his player gets the ball alone in our box with Dembele 2 meters behind him even though Dembele was marking a player only 5 seconds, before he "fell asleep" and watched the action at the other side of a box.
In one of those actions, he made a tackle.
But he created both chances for Chelsea.
An analogy would be:
MATS dribbling a player in our box and losing a ball.
An opponent hesitates and attempts a shot.
MATS saves the shot in the end.
Ok, a nice save, but he shouldn't have dribbled and allowed a chance in the first place.
So, he didn't "save" it.
He created/ruined it and THEN saved it.