He wasn't in the wall. He was the other side of Caicedo, more than 1m from the wall.
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Then he pushes Caicedo sideways and is now within 1m of the wall (and Eze still hasn't got to the ball yet)
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Clear breach of this "1m" rule, even when the ref doesn't give a foul against Guehi for the shove on Caicedo, which he should give in my opinion, as the goal doesn't happen if Caicedo stays where he is (the ball would have hit him). The ball goes through the gap that Guehi creates with the push.